Consolidated Statements of Changes in Equity (Unaudited) (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Total shareholders' Equity [Member]	Non-Controlling Interest [Member]
Balances at Dec. 31, 2010	$ 2,543,878	$ 4	$ 107,839	$ 782,805	$ 1,743,880	$ (112,802)	$ 2,521,726	$ 22,152
Balances (in shares) at Dec. 31, 2010		70,816				2,608
Comprehensive income:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	136,461	0	0	0	133,781	0	133,781	2,680
Other comprehensive income, net of tax	38,416	0	38,416	0	0	0	38,416	0
Exercise of stock options (in shares)		284				30
Exercise of stock options	4,291	0	0	6,345	0	(2,054)	4,291	0
Tax benefit on exercise of stock options	339	0	0	339	0	0	339	0
Stock-based compensation	4,803
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4,803	0	0	4,803	0	0	4,803	0
Cash dividends on common stock	(35,639)	0	0	0	(35,639)	0	(35,639)	0
Capital calls and distributions, net	(375)	0	0	0	0	0	0	(375)
Balances at Jun. 30, 2011	2,692,174	4	146,255	794,292	1,842,022	(114,856)	2,667,717	24,457
Balances (in shares) at Jun. 30, 2011		71,100				2,638
Balances at Dec. 31, 2011	2,786,652	4	128,979	818,817	1,953,332	(150,664)	2,750,468	36,184
Balances (in shares) at Dec. 31, 2011		71,533				3,380
Comprehensive income:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	182,654	0	0	0	181,243	0	181,243	1,411
Other comprehensive income, net of tax	10,211	0	10,211	0	0	0	10,211	0
Treasury stock purchases (in shares)		0				384
Treasury stock purchases	(20,558)					(20,558)	(20,558)	0
Exercise of stock options (in shares)		473				98
Exercise of stock options	8,454	0	0	13,122	0	(4,668)	8,454	0
Tax benefit on exercise of stock options	(677)	0	0	(677)	0	0	(677)	0
Stock-based compensation	4,803
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	4,803	0	0	4,803	0	0	4,803	0
Cash dividends on common stock	(48,010)	0	0	0	(48,010)	0	(48,010)	0
Capital calls and distributions, net	(808)	0	0	0	0	0	0	(808)
Balances at Jun. 30, 2012	$ 2,922,721	$ 4	$ 139,190	$ 836,065	$ 2,086,565	$ (175,890)	$ 2,885,934	$ 36,787
Balances (in shares) at Jun. 30, 2012		72,006				3,862