Consolidated Statements of Changes in Equity (USD $) 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 at Dec. 31, 2011	$ 2,786,652	$ 4	$ 818,817	$ 1,953,332	$ (150,664)	$ 128,979	$ 2,750,468	$ 36,184
Balances (in shares) at Dec. 31, 2011		71,533			3,380
Net income	354,124			351,191			351,191	2,933
Other comprehensive income (loss)	20,941					20,941	20,941
Repurchase of common stock (in shares)					384
Repurchase of common stock	(20,558)				(20,558)		(20,558)
Issuance of shares for equity compensation, net (in shares)		882			324
Issuance of shares for equity compensation, net	14,650		32,311		(17,661)		14,650
Tax effect from equity compensation, net	120		120				120
Share-based compensation	8,030		8,030				8,030
Issuance of shares in settlement of deferred compensation, net	0
Cash dividends on common stock	(166,982)			(166,982)			(166,982)
Acquisition of non-controlling interest	1,645							1,645
Capital calls and distributions, net	(4,941)							(4,941)
Balance, end of period at Dec. 31, 2012	2,993,681	4	859,278	2,137,541	(188,883)	149,920	2,957,860	35,821
Balances (in shares) at Dec. 31, 2012		72,415			4,088
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
Issuance of shares in settlement of deferred compensation, net	0
Cash dividends on common stock	(104,722)			(104,722)			(104,722)
Capital calls and distributions, net	(3,219)							(3,219)
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
Balances (in shares) at Dec. 31, 2013		73,163			4,305
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 (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 at Dec. 31, 2014	$ 3,336,206	$ 4	$ 954,644	$ 2,530,837	$ (239,979)	$ 56,673	$ 3,302,179	$ 34,027
Balances (in shares) at Dec. 31, 2014		74,004			4,890