CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) (USD $) In Thousands, unless otherwise specified	Common stock [Member]	Paid-in capital [Member]	Treasury stock [Member]	Accumulated other comprehensive income (loss) [Member]	Retained earnings (deficit) [Member]	Total
Balance at Dec. 31, 2013	$ 340,047	$ 1,661,269	$ (64,435)	$ (117,726)	$ (1,074,617)	$ 744,538
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	59,982	59,982
Change in unrealized investment gains and losses, net	0	0	0	39,598	0	39,598
Reissuance of treasury stock, net	0	(5,712)	30,530	0	(29,791)	(4,973)
Equity compensation	0	1,803	0	0	0	1,803
Benefit plan adjustments	0	0	0	(1,486)	0	(1,486)
Unrealized foreign currency translation adjustment, net	0	0	0	1,253	0	1,253
Balance at Mar. 31, 2014	340,047	1,657,360	(33,905)	(78,361)	(1,044,426)	840,715
Balance at Dec. 31, 2014	340,047	1,663,592	(32,937)	(81,341)	(852,458)	1,036,903
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	0	0	0	0	133,076	133,076
Change in unrealized investment gains and losses, net	0	0	0	19,563	0	19,563
Net common stock issued under share-based compensation plans	32	38	0	0	0	70
Reissuance of treasury stock, net	0	(7,251)	29,575	0	(29,494)	(7,170)
Tax benefit from share-based compensation	0	2,568	0	0	0	2,568
Equity compensation	0	3,264	0	0	0	3,264
Benefit plan adjustments	0	0	0	(700)	0	(700)
Unrealized foreign currency translation adjustment, net	0	0	0	(2,014)	0	(2,014)
Balance at Mar. 31, 2015	$ 340,079	$ 1,662,211	$ (3,362)	$ (64,492)	$ (748,876)	$ 1,185,560