Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Series C Preferred Stock [Member]	Series D Preferred Stock [Member]	Parent [Member]	Parent [Member] Series C Preferred Stock [Member]	Parent [Member] Series D Preferred Stock [Member]	Preferred Stock [Member] Series C Preferred Stock [Member]	Preferred Stock [Member] Series D Preferred Stock [Member]	Common Stock [Member]	Capital in Excess of Par Value [Member]	Capital in Excess of Par Value [Member] Series C Preferred Stock [Member]	Capital in Excess of Par Value [Member] Series D Preferred Stock [Member]	Retained Earnings [Member]	Retained Earnings [Member] Series C Preferred Stock [Member]	Retained Earnings [Member] Series D Preferred Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Balances at Dec. 31, 2009	$ 1,566,862			$ 1,564,240			$ 92,000	$ 0	$ 825	$ 1,408,491			$ 62,413			$ 511	$ 2,622
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	73,353			72,997									72,997				356
Dividends declared and paid:
Preferred stock dividends declared and paid		(6,785)			(6,785)									(6,785)
Common stock dividends declared and paid	(118,038)			(118,038)					3	7,350			(125,391)
Redemption of 3,680,000 shares of Series C Preferred Stock	0
Issuance of common stock:
Issuance of common stock	698			698					1	697
Issuance of common stock - stock purchase program	10,277			10,277					5	10,272
Issuance of shares of restricted common stock									4	(4)
Stock issuance costs	(1)			(1)						(1)
Performance incentive plan	(1,634)			(1,634)						(1,634)
Amortization of deferred compensation	5,119			5,119						5,119
Amortization of interest rate hedges	(165)			(165)												(165)
Unrealized gain/loss – commercial mortgage residual interests	1,246			1,272												1,272	(26)
Fair value treasury locks	0
Stock value adjustments	17
Contributions from noncontrolling interests	43																43
Distributions to noncontrolling interests	(861)																(861)
Purchase of noncontrolling interest	(1,603)			(404)						(404)							(1,199)
Other	263			(93)						(136)						43	356
Balances at Dec. 31, 2010	1,528,774			1,527,483			92,000	0	838	1,429,750			3,234			1,661	1,291
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	92,416			92,325									92,325				91
Dividends declared and paid:
Preferred stock dividends declared and paid		(6,785)			(6,785)									(6,785)
Common stock dividends declared and paid	(120,063)			(120,063)					5	13,652			(133,720)
Redemption of 3,680,000 shares of Series C Preferred Stock	0
Issuance of common stock:
Issuance of common stock	447,863			447,863					173	447,690
Issuance of common stock - stock purchase program	79,794			79,794					32	79,762
Issuance of shares of restricted common stock	(56)			(56)					1	(57)
Stock issuance costs	(19,453)			(19,453)						(19,453)
Performance incentive plan	(513)			(513)						(513)
Amortization of deferred compensation	7,394			7,394						7,394
Amortization of interest rate hedges	9			9												9
Unrealized gain/loss – commercial mortgage residual interests	(246)			(246)												(246)
Fair value treasury locks	(5,218)			(5,218)												(5,218)
Stock value adjustments	(36)			(36)												(36)
Contributions from noncontrolling interests	41																41
Distributions to noncontrolling interests	(45)																(45)
Balances at Dec. 31, 2011	2,003,876			2,002,498			92,000	0	1,049	1,958,225			(44,946)			(3,830)	1,378
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	141,937			142,015									142,015				(78)
Dividends declared and paid:
Preferred stock dividends declared and paid		(1,979)	(15,449)		(1,979)	(15,449)								(1,979)	(15,449)
Common stock dividends declared and paid	(155,733)			(155,733)					4	11,758			(167,495)
Redemption of 3,680,000 shares of Series C Preferred Stock	(3,098)	(92,000)			(92,000)		(92,000)				3,098			(3,098)
Issuance of common stock:
Issuance of common stock	833		277,645	833		277,645		287,500		833		(9,855)
Issuance of common stock - stock purchase program	44,412			44,412					17	44,395
Issuance of common stock - ATM equity program	129,092			129,092					43	129,049
Issuance of shares of restricted common stock	335			335					4	331
Equity component of convertible debt	(41,486)			(41,486)						(41,486)
Stock issuance costs	(2,265)			(2,265)						(2,265)
Performance incentive plan	(451)			(451)						(451)
Amortization of deferred compensation	7,370			7,370						7,370
Amortization of interest rate hedges	231			231												231
Unrealized gain/loss – commercial mortgage residual interests	1,132			1,132												1,132
Fair value treasury locks	0
Stock value adjustments	85			85												85
Balances at Dec. 31, 2012	$ 2,297,585			$ 2,296,285			$ 0	$ 287,500	$ 1,117	$ 2,101,002			$ (90,952)			$ (2,382)	$ 1,300