Consolidated Statements of Net Proceeds From All Sources - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |||||
|---|---|---|---|---|---|---|---|
Dec. 31, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Mar. 31, 2017 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Balances | Ìý | $ 105,098 | Ìý | $ 52,659 | $ 105,098 | $ 52,659 | $ 45,687 |
| Net income | $ 62,680 | $ 43,791 | $ 24,620 | $ 19,259 | 209,736 | 97,231 | 42,275 |
| Periodic pension costs, net of income taxes | Ìý | Ìý | Ìý | Ìý | (94) | 156 | 289 |
| Repurchase and retirement of Sub-share Certificates in Certificates of Proprietary Interest | Ìý | Ìý | Ìý | Ìý | (38,397) | (34,267) | (33,085) |
| Dividends paid | Ìý | Ìý | Ìý | Ìý | (8,206) | (2,769) | (2,507) |
| Special dividends paid | Ìý | Ìý | Ìý | Ìý | (23,446) | (7,912) | Ìý |
| Balances | $ 244,691 | Ìý | $ 105,098 | Ìý | $ 244,691 | $ 105,098 | $ 52,659 |
| Sub-share Certificates of Proprietary Interest | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Balances (in shares) | Ìý | 7,821,599 | Ìý | 7,927,314 | 7,821,599 | 7,927,314 | 8,118,064 |
| Repurchase and retirement of Sub-share Certificates in Certificates of Proprietary Interest (in shares) | Ìý | Ìý | Ìý | Ìý | (59,185) | (105,715) | (190,750) |
| Balances (in shares) | 7,762,414 | Ìý | 7,821,599 | Ìý | 7,762,414 | 7,821,599 | 7,927,314 |
| Accumulated Other Comprehensive Income (Loss) | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Balances | Ìý | $ (804) | Ìý | $ (960) | $ (804) | $ (960) | $ (1,249) |
| Periodic pension costs, net of income taxes | Ìý | Ìý | Ìý | Ìý | (274) | 156 | 289 |
| Repurchase and retirement of Sub-share Certificates in Certificates of Proprietary Interest | Ìý | Ìý | Ìý | Ìý | Ìý | 0 | Ìý |
| Balances | $ (1,078) | Ìý | $ (804) | Ìý | (1,078) | (804) | (960) |
| Net Proceeds From All Sources | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
| Balances | Ìý | $ 105,902 | Ìý | $ 53,619 | 105,902 | 53,619 | 46,936 |
| Net income | Ìý | Ìý | Ìý | Ìý | 209,736 | 97,231 | 42,275 |
| Periodic pension costs, net of income taxes | Ìý | Ìý | Ìý | Ìý | 180 | Ìý | Ìý |
| Repurchase and retirement of Sub-share Certificates in Certificates of Proprietary Interest | Ìý | Ìý | Ìý | Ìý | (38,397) | (34,267) | (33,085) |
| Dividends paid | Ìý | Ìý | Ìý | Ìý | (8,206) | (2,769) | (2,507) |
| Special dividends paid | Ìý | Ìý | Ìý | Ìý | (23,446) | (7,912) | Ìý |
| Balances | $ 245,769 | Ìý | $ 105,902 | Ìý | $ 245,769 | $ 105,902 | $ 53,619 |
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- Definition Amount of paid and unpaid special cash dividends declared for classes of stock, for example, but not limited to, common and preferred. No definition available.
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- Definition Amount of paid and unpaid cash dividends declared for classes of stock, for example, but not limited to, common and preferred. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Amount, after tax, of cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Number of shares issued which are neither cancelled nor held in the treasury. No definition available.
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- Definition Number of shares that have been repurchased and retired during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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