Consolidated Statements Of Changes In Equity (USD $) In Thousands	Total	Total Equity [Domain]	Total Shareholders' Equity [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Noncontrolling Interests [Member]	Redeemable Noncontrolling Interests [Member]
Balance at Dec. 31, 2010		$ 3,172,394	$ 3,171,523	$ 884,457	$ 1,735,973	$ 551,093	$ 871
Balance, redeemable noncontrolling interests at Dec. 31, 2010								15,298
Net income (loss)	96,179	91,505	91,850		91,850	0	(345)	4,674
Change in net unrealized gains on investments, net of taxes	(19,235)	(19,235)	(19,235)		0	(19,235)	0	0
Change in foreign currency translation adjustments, net of taxes	(5,538)	(5,538)	(5,538)		0	(5,538)	0	0
Change in net actuarial pension loss, net of taxes	1,080	1,080	1,080		0	1,080	0	0
Comprehensive Income (Loss)	72,486	67,812	68,157				(345)	4,674
Issuance of common stock		1,182	1,182	1,182	0	0	0	0
Repurchase of common stock		(33,436)	(33,436)	0	(33,436)	0	0	0
Restricted stock units expensed		4,606	4,606	4,606	0	0	0	0
Acquisitions		0	0	0	0	0	0	47,287
Other		148	148	148	0	0	0	(1,873)
Balance, redeemable noncontrolling interests at Sep. 30, 2011								65,386
Balance at Sep. 30, 2011		3,212,706	3,212,180	890,393	1,794,387	527,400	526
Balance at Dec. 31, 2011	3,388,115	3,388,115	3,387,513	891,507	1,835,086	660,920	602
Balance, redeemable noncontrolling interests at Dec. 31, 2011	74,231							74,231
Net income (loss)	200,155	195,851	196,593		196,593	0	(742)	4,304
Change in net unrealized gains on investments, net of taxes	225,766	225,766	225,766		0	225,766	0	0
Change in foreign currency translation adjustments, net of taxes	2,927	2,969	2,969		0	2,969	0	(42)
Change in net actuarial pension loss, net of taxes	1,487	1,487	1,487		0	1,487	0	0
Comprehensive Income (Loss)	430,335	426,073	426,815				(742)	4,262
Issuance of common stock		8,803	8,803	8,803	0	0	0	0
Repurchase of common stock		(16,062)	(16,062)	0	(16,062)	0	0	0
Restricted stock units expensed		5,184	5,184	5,184	0	0	0	0
Acquisitions		0	0	0	0	0	0	7,896
Adjustment of redeemable noncontrolling interests	6,500	(6,484)	(6,484)	0	(6,484)	0	0	6,484
Other		290	347	347	0	0	(57)	(5,135)
Balance, redeemable noncontrolling interests at Sep. 30, 2012	87,738							87,738
Balance at Sep. 30, 2012	$ 3,805,919	$ 3,805,919	$ 3,806,116	$ 905,841	$ 2,009,133	$ 891,142	$ (197)