Consolidated Statements Of Changes In Equity - USD ($) shares in Thousands, $ in Thousands	Total	Total Equity [Member]	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, 2012		$ 3,889,017	$ 3,888,657	$ 908,980	$ 2,068,340	$ 911,337	$ 360
Balance, shares at Dec. 31, 2012				9,629
Balance, redeemable noncontrolling interests at Dec. 31, 2012								$ 86,225
Net income (loss)	$ 283,845	280,063	281,021		281,021	0	(958)	3,782
Other comprehensive income (loss)	178,496	178,468	178,468		0	178,468	0	28
Comprehensive Income	462,341	458,531	459,489				(958)	3,810
Issuance of common stock		24,518	24,518	$ 24,518	0	0	0	0
Issuance of common stock, shares				71
Repurchase of common stock		(57,388)	(57,388)	$ 0	(57,388)	0	0	0
Repurchase of common stock, shares				(109)
Restricted stock awards expensed		25,239	25,239	$ 25,239	0	0	0	0
Restricted stock awards expensed, shares				(3)
Acquisition of Alterra		2,330,199	2,330,199	$ 2,330,199	0	0	0	0
Acquisition of Alterra, shares				4,398
Adjustment of redeemable noncontrolling interests		1,963	1,963	$ 0	1,963	0	0	(1,963)
Adjustment of redeemable noncontrolling interests, shares				0
Purchase of noncontrolling interest		(136)	(136)	$ (136)	0	0	0	(11,716)
Purchase of noncontrolling interest, shares				0
Other		6,067	1,036	$ 63	973	0	5,031	(4,173)
Other, shares				0
Balance at Dec. 31, 2013		6,678,010	6,673,577	$ 3,288,863	2,294,909	1,089,805	4,433
Balance, shares at Dec. 31, 2013				13,986
Balance, redeemable noncontrolling interests at Dec. 31, 2013								72,183
Net income (loss)	323,688	319,201	321,182		321,182	0	(1,981)	4,487
Other comprehensive income (loss)	614,756	614,752	614,752		0	614,752	0	4
Comprehensive Income	938,444	933,953	935,934				(1,981)	4,491
Issuance of common stock		5,691	5,691	$ 5,691	0	0	0	0
Issuance of common stock, shares				19
Repurchase of common stock		(26,053)	(26,053)	$ 0	(26,053)	0	0	0
Repurchase of common stock, shares				(43)
Restricted stock awards expensed		22,935	22,935	$ 22,935	0	0	0	0
Restricted stock awards expensed, shares				0
Adjustment of redeemable noncontrolling interests		(8,186)	(8,186)	$ 0	(8,186)	0	0	8,186
Adjustment of redeemable noncontrolling interests, shares				0
Purchase of noncontrolling interest		(9,352)	(10,257)	$ (10,257)	0	0	905	(18,566)
Purchase of noncontrolling interest, shares				0
Other		5,004	1,177	$ 1,163	14	0	3,827	(5,246)
Other, shares				0
Balance at Dec. 31, 2014	7,602,002	7,602,002	7,594,818	$ 3,308,395	2,581,866	1,704,557	7,184
Balance, shares at Dec. 31, 2014				13,962
Balance, redeemable noncontrolling interests at Dec. 31, 2014	61,048							61,048
Net income (loss)	589,142	581,784	582,772		582,772	0	(988)	7,358
Other comprehensive income (loss)	(350,122)	(350,049)	(350,049)		0	(350,049)	0	(73)
Comprehensive Income	239,020	231,735	232,723				(988)	7,285
Issuance of common stock		4,752	4,752	$ 4,752	0	0	0	0
Issuance of common stock, shares				34
Repurchase of common stock		(31,491)	(31,491)	$ 0	(31,491)	0	0	0
Repurchase of common stock, shares				(37)
Restricted stock awards expensed		24,129	24,129	$ 24,129	0	0	0	0
Restricted stock awards expensed, shares				0
Acquisition of CapTech		0	0	$ 0	0	0	0	13,817
Acquisition of CapTech, shares				0
Adjustment of redeemable noncontrolling interests		4,144	4,144	$ 0	4,144	0	0	(4,144)
Adjustment of redeemable noncontrolling interests, shares				0
Purchase of noncontrolling interest		(1,447)	(1,447)	$ (1,447)	0	0	0	(8,224)
Purchase of noncontrolling interest, shares				0
Other		6,785	6,522	$ 6,528	(6)	0	263	(6,824)
Other, shares				0
Balance at Dec. 31, 2015	7,840,609	$ 7,840,609	$ 7,834,150	$ 3,342,357	$ 3,137,285	$ 1,354,508	$ 6,459
Balance, shares at Dec. 31, 2015				13,959
Balance, redeemable noncontrolling interests at Dec. 31, 2015	$ 62,958							$ 62,958