Consolidated Statements of Stockholders' Equity (USD $)	Total	Series C Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Stockholders' Equity, Total [Member]	Noncontrolling Interest [Member]	Series C Preferred Stock [Member]
Balances at Dec. 31, 2008	$ 1,568,946,000		$ 784,000	$ 1,337,018,000	$ 134,644,000	$ 2,414,000	$ 1,566,860,000	$ 2,086,000	$ 92,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	56,399,000				54,810,000		54,810,000	1,589,000
Dividends declared and paid:
1.84375 per depositary share of Series C preferred stock	(6,785,000)				(6,785,000)		(6,785,000)
Dividends, Common stock	(118,458,000)		1,000	1,797,000	(120,256,000)		(118,458,000)
Stock Issued During Period, Value, New Issues	1,436,000		1,000	1,435,000			1,436,000
Shares - discounted stock purchase program	65,555,000		36,000	65,519,000			65,555,000
Stock Issued During Period, Value, Restricted Stock Award, Gross			3,000	(3,000)
Stock Issuance Costs	(113,000)			(113,000)			(113,000)
Equity component of convertible debt	(795,000)			(795,000)			(795,000)
Amortization of deferred compensation	3,443,000			3,443,000			3,443,000
Amortization Of Interest Rate Hedges	(159,000)					(159,000)	(159,000)
Unrealized gain - commercial mortgage residual interests	(1,640,000)					(1,744,000)	(1,744,000)	104,000
Contributions from noncontrolling interests	152,000							152,000
Distributions to noncontrolling interests	(552,000)							(552,000)
Other	(567,000)			190,000			190,000	(757,000)
Balances at Dec. 31, 2009	1,566,862,000	92,000,000	825,000	1,408,491,000	62,413,000	511,000	1,564,240,000	2,622,000	92,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	73,353,000				72,997,000		72,997,000	356,000
Dividends declared and paid:
1.84375 per depositary share of Series C preferred stock	(6,785,000)				(6,785,000)		(6,785,000)
Dividends, Common stock	(118,038,000)		3,000	7,350,000	(125,391,000)		(118,038,000)
Stock Issued During Period, Value, New Issues	698,000		1,000	697,000			698,000
Shares - discounted stock purchase program	10,277,000		5,000	10,272,000			10,277,000
Stock Issued During Period, Value, Restricted Stock Award, Gross			4,000	(4,000)
Stock Issuance Costs	(1,000)			(1,000)			(1,000)
Performance Incentive Plans	(1,634,000)			(1,634,000)			(1,634,000)
Amortization of deferred compensation	5,119,000			5,119,000			5,119,000
Amortization Of Interest Rate Hedges	(165,000)					(165,000)	(165,000)
Unrealized gain - commercial mortgage residual interests	1,246,000					1,272,000	1,272,000	(26,000)
Contributions from noncontrolling interests	43,000							43,000
Distributions to noncontrolling interests	(861,000)							(861,000)
Purchase of noncontrolling interest	(1,603,000)			(404,000)			(404,000)	(1,199,000)
Other	263,000			(136,000)		43,000	(93,000)	356,000
Balances at Dec. 31, 2010	1,528,774,000	92,000,000	838,000	1,429,750,000	3,234,000	1,661,000	1,527,483,000	1,291,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	92,416,000				92,325,000		92,325,000	91,000
Dividends declared and paid:
1.84375 per depositary share of Series C preferred stock	(6,785,000)				(6,785,000)		(6,785,000)
Dividends, Common stock	(120,063,000)		5,000	13,652,000	(133,720,000)		(120,063,000)
Stock Issued During Period, Value, New Issues	447,863,000		173,000	447,690,000			447,863,000
Shares - discounted stock purchase program	79,794,000		32,000	79,762,000			79,794,000
Stock Issued During Period, Value, Restricted Stock Award, Gross	(56,000)		1,000	(57,000)			(56,000)
Stock Issuance Costs	(19,453,000)			(19,453,000)			(19,453,000)
Performance Incentive Plans	(513,000)			(513,000)			(513,000)
Amortization of deferred compensation	7,394,000			7,394,000			7,394,000
Amortization Of Interest Rate Hedges	9,000					9,000	9,000
Unrealized gain - commercial mortgage residual interests	(246,000)					(246,000)	(246,000)
Stock value adjustment	(36,000)					(36,000)	(36,000)
Contributions from noncontrolling interests	41,000							41,000
Distributions to noncontrolling interests	(45,000)							(45,000)
Balances at Dec. 31, 2011	$ 2,003,876,000	$ 92,000,000	$ 1,049,000	$ 1,958,225,000	$ (44,946,000)	$ (3,830,000)	$ 2,002,498,000	$ 1,378,000