Consolidated Statements of Changes in Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total Shareholders' Equity [Member]	Non-Controlling Interests [Member]
Balance, beginning of period (in shares) at Dec. 31, 2012		72,415			4,088
Balance, beginning of period at Dec. 31, 2012	$ 2,993,681	$ 4	$ 859,278	$ 2,137,541	$ (188,883)	$ 149,920	$ 2,957,860	$ 35,821
Net income	318,931			316,609			316,609	2,322
Other comprehensive income (loss)	(175,543)					(175,543)	(175,543)
Repurchase of common stock (in shares)					0
Repurchase of common stock	0				$ 0		0
Issuance of shares for equity compensation, net (in shares)		748			217
Issuance of shares for equity compensation, net	16,566		30,029		$ (13,463)		16,566
Tax effect from equity compensation, net	2,210		2,210				2,210
Share-based compensation	7,069		7,069				7,069
Cash dividends on common stock	(104,722)			(104,722)			(104,722)
Capital calls and distributions, net	(3,219)							(3,219)
Balance, end of period (in shares) at Dec. 31, 2013		73,163			4,305
Balance, end of period at Dec. 31, 2013	3,054,973	$ 4	898,586	2,349,428	$ (202,346)	(25,623)	3,020,049	34,924
Net income	295,479			292,435			292,435	3,044
Other comprehensive income (loss)	82,296					82,296	82,296
Repurchase of common stock (in shares)					200
Repurchase of common stock	(12,337)				$ (12,337)		(12,337)
Issuance of shares for equity compensation, net (in shares)		510			183
Issuance of shares for equity compensation, net	4,472		16,632		$ (12,160)		4,472
Tax effect from equity compensation, net	8,258		8,258				8,258
Share-based compensation	9,680		9,680				9,680
Issuance of shares in settlement of deferred compensation, net (in shares)		331			202
Issuance of shares in settlement of deferred compensation, net	8,352		21,488		$ (13,136)		8,352
Cash dividends on common stock	(111,026)			(111,026)			(111,026)
Capital calls and distributions, net	(3,941)							(3,941)
Balance, end of period (in shares) at Dec. 31, 2014		74,004			4,890
Balance, end of period at Dec. 31, 2014	3,336,206	$ 4	954,644	2,530,837	$ (239,979)	56,673	3,302,179	34,027
Net income	292,259			288,565			288,565	3,694
Other comprehensive income (loss)	(35,086)					(35,086)	(35,086)
Repurchase of common stock (in shares)					3,634
Repurchase of common stock	(229,540)				$ (229,540)		(229,540)
Issuance of shares for equity compensation, net (in shares)		526			112
Issuance of shares for equity compensation, net	6,711		14,357		$ (7,646)		6,711
Tax effect from equity compensation, net	925		925				925
Share-based compensation	12,083		12,083				12,083
Cash dividends on common stock	(115,281)			(115,281)			(115,281)
Sale of non-controlling interest	5,500							5,500
Capital calls and distributions, net	(6,138)							(6,138)
Balance, end of period (in shares) at Dec. 31, 2015		74,530			8,636
Balance, end of period at Dec. 31, 2015	$ 3,267,639	$ 4	$ 982,009	$ 2,704,121	$ (477,165)	$ 21,587	$ 3,230,556	$ 37,083