CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Noncontrolling Interests [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Deficit) [Member]	Accumulated Comprehensive Income [Member]	Treasury Stock [Member]	Total	Redeemable Noncontrolling Interests [Member]
Balance at Dec. 31, 2014	$ 2,734	$ 33	$ 291,681	$ 602,950	$ 25,014	$ (394,617)	$ 527,795	$ 68,334
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Redemptions of noncontrolling interests	0	0	0	0	0	0	0	0
Contributions from redeemable noncontrolling interests	0	0	0	0	0	0	0	0
Net income	0	0	0	83,412	0	0	83,412	0
Net unrealized gains (losses) on securities available for sale, net of income tax expense (benefit)	0	0	0	0	(5,471)	0	(5,471)	0
Amounts reclassified from accumulated other comprehensive income, net of income tax expense (benefit)	0	0	0	0	(2,829)	0	(2,829)	0
Foreign currency translation	0	0	0	0	(46)	0	(46)	0
Dividends declared	0	0	0	(7,477)	0	0	(7,477)	0
Stock based compensation expense	0	0	9,868	0	0	0	9,868	0
Reduction of deferred tax asset for excess of recorded RSA tax benefit over actual tax benefit	0	0	(1,190)	0	0	0	(1,190)	0
Exercise of stock options including tax benefit ($102)	0	0	1,269	0	0	0	1,269	0
Purchase of treasury stock	0	0	0	0	0	(27,249)	(27,249)	0
Issuance of 4.4 million treasury shares to GSI	0	0	(20,270)	0	0	170,270	150,000	0
Spin-off of AC	(2,734)	0	(281,013)	(713,109)	(7,553)	0	(1,004,409)	(68,334)
Balance at Dec. 31, 2015	$ 0	33	345	(34,224)	9,115	(251,596)	(276,327)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		0	0	117,121	0	0	117,121
Net unrealized gains (losses) on securities available for sale, net of income tax expense (benefit)		0	0	0	3,111	0	3,111
Amounts reclassified from accumulated other comprehensive income, net of income tax expense (benefit)		0	0	0	(791)	0	(791)
Foreign currency translation		0	0	0	(164)	0	(164)
Dividends declared		0	0	(2,382)	0	0	(2,382)
Stock based compensation expense		0	3,959	0	0	0	3,959
Reduction of deferred tax asset for excess of recorded RSA tax benefit over actual tax benefit		0	(401)	0	0	0	(401)
Purchase of treasury stock		0	0	0	0	(10,773)	(10,773)
Balance at Dec. 31, 2016		33	3,903	80,515	11,271	(262,369)	(166,647)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		0	0	77,809	0	0	77,809
Net unrealized gains (losses) on securities available for sale, net of income tax expense (benefit)		0	0	0	2,492	0	2,492
Amounts reclassified from accumulated other comprehensive income, net of income tax expense (benefit)		0	0	0	(1,969)	0	(1,969)
Foreign currency translation		0	0	0	82	0	82
Dividends declared		0	0	(2,385)	0	0	(2,385)
Stock based compensation expense		0	8,669	0	0	0	8,669
Purchase of treasury stock		0	0	0	0	(14,324)	(14,324)
Balance at Dec. 31, 2017		$ 33	$ 12,572	$ 155,939	$ 11,876	$ (276,693)	$ (96,273)