Consolidated Statements Of Changes In Equity (USD $) In Thousands	Total	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Total Shareholders' Equity [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2010	$ 3,187,692	$ 884,457	$ 1,735,973	$ 551,093	$ 3,171,523	$ 16,169
Net income	9,861		8,272	0	8,272	1,589
Change in net unrealized gains on investments, net of taxes	13,681		0	13,681	13,681	0
Change in foreign currency translation adjustments, net of taxes	2,439		0	2,439	2,439	0
Change in net actuarial pension loss, net of taxes	346		0	346	346	0
Comprehensive Income	26,327				24,738	1,589
Issuance of common stock	163	163	0	0	163	0
Restricted stock units expensed	1,902	1,902	0	0	1,902	0
Acquisitions	47,292	0	0	0	0	47,292
Other	(307)	52	0	0	52	(359)
Balance at Mar. 31, 2011	3,263,069	886,574	1,744,245	567,559	3,198,378	64,691
Balance at Dec. 31, 2011	3,462,346	891,507	1,835,086	660,920	3,387,513	74,833
Net income	57,713		57,253	0	57,253	460
Change in net unrealized gains on investments, net of taxes	145,386		0	145,386	145,386	0
Change in foreign currency translation adjustments, net of taxes	2,823		0	2,823	2,823	0
Change in net actuarial pension loss, net of taxes	483		0	483	483	0
Comprehensive Income	206,405				205,945	460
Issuance of common stock	8,274	8,274	0	0	8,274	0
Restricted stock units expensed	2,366	2,366	0	0	2,366	0
Repurchase of common stock	(2,299)	0	(2,299)	0	(2,299)	0
Other	(1,124)	294	0	0	294	(1,418)
Balance at Mar. 31, 2012	$ 3,675,968	$ 902,441	$ 1,890,040	$ 809,612	$ 3,602,093	$ 73,875