Consolidated Statements of Stockholders' Equity and Noncontrolling Interest (USD $) In Thousands, except Share data, unless otherwise specified	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Distributions in Excess of Accumulated Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Total
Balances at Dec. 31, 2009	$ 25,000	$ 3	$ 1,275,251	$ (222,952)	$ (24,206)	$ 220,445	$ 1,273,541
Balances (in shares) at Dec. 31, 2009	1,000,000	28,849,000
Net income	0	0	0	35,934	0	14,848	50,782
Reversal of unrealized gains upon the sale of marketable securities	0	0	0	0	(11,163)	(864)	(12,027)
Changes in fair value of cash flow hedges and amortization of settlement swaps	0	0	0	0	(46,817)	(3,620)	(50,437)
Changes in fair value of marketable securities	0	0	0	0	4,969	388	5,357
Issuance of common stock under:
Stock option plans	0	0	5,803	0	0	0	5,803
Stock option plans (in shares)		122,000
Sale of common stock	0	0	251,455	0	0	0	251,455
Sale of common stock (in shares)		2,354,000
Equity based compensation costs	0	0	(260)	0	0	2,474	2,214
Retirement of exchangeable bonds	0	0	(434)	0	0	0	(434)
Contributions of noncontrolling interest	0	0	0	0	0	4,038	4,038
Redemptions of noncontrolling interest	0	0	(16,347)	0	0	(7,839)	(24,186)
Distributions to noncontrolling interest	0	0	0	0	0	(24,802)	(24,802)
Common and preferred stock dividends declared	0	0	0	(126,290)	0	0	(126,290)
Balances at Dec. 31, 2010	25,000	3	1,515,468	(313,308)	(77,217)	205,068	1,355,014
Balances (in shares) at Dec. 31, 2010	1,000,000	31,325,000
Net income	0	0	0	47,070	0	10,446	57,516
Reversal of unrealized gains upon the sale of marketable securities	0	0	0	0	(4,011)	(275)	(4,286)
Changes in fair value of cash flow hedges and amortization of settlement swaps	0	0	0	0	7,212	495	7,707
Changes in fair value of marketable securities	0	0	0	0	1,245	85	1,330
Issuance of common stock under:
Stock option plans	0	0	8,412	0	0	0	8,412
Stock option plans (in shares)		103,000
Sale of common stock	0	0	323,931	0	0	0	323,931
Sale of common stock (in shares)		2,460,000
Equity based compensation costs	0	0	(725)	0	0	1,598	873
Issuance of Series H Preferred	73,750	0	(2,541)	0	0	0	71,209
Issuance of Series H Preferred (in shares)	2,950,000
Redemptions of Series F Preferred	(25,000)	0	0	0	0	0	(25,000)
Redemptions of Series F Preferred (in shares)	(1,000,000)
Redemptions of Series B Preferred	0	0	1,200	0	0	(80,000)	(78,800)
Redemptions of noncontrolling interest	0	0	(1,134)	0	0	(4,253)	(5,387)
Distributions to noncontrolling interest	0	0	0	0	0	(16,963)	(16,963)
Common and preferred stock dividends declared	0	0	0	(141,828)	0	0	(141,828)
Balances at Dec. 31, 2011	73,750	3	1,844,611	(408,066)	(72,771)	116,201	1,553,728
Balances (in shares) at Dec. 31, 2011	2,950,000	33,888,000
Net income	0	0	0	125,284	0	14,306	139,590
Reversal of unrealized gains upon the sale of marketable securities	0	0	0	0	(1,018)	(64)	(1,082)
Changes in fair value of cash flow hedges and amortization of settlement swaps	0	0	0	0	3,183	219	3,402
Changes in fair value of marketable securities	0	0	0	0	1,345	66	1,411
Issuance of common stock under:
Stock option plans	0	0	4,675	0	0	0	4,675
Stock option plans (in shares)		151,000
Sale of common stock	0	0	357,720	0	0	0	357,720
Sale of common stock (in shares)		2,404,000
Equity based compensation costs	0	0	(430)	0	0	2,231	1,801
Contributions of noncontrolling interest	0	0	0	0	0	4,232	4,232
Redemptions of noncontrolling interest	0	0	(1,798)	0	0	(5,188)	(6,986)
Distributions to noncontrolling interest	0	0	0	0	0	(16,691)	(16,691)
Common and preferred stock dividends declared	0	0	0	(161,684)	0	0	(161,684)
Balances at Dec. 31, 2012	$ 73,750	$ 3	$ 2,204,778	$ (444,466)	$ (69,261)	$ 115,312	$ 1,880,116
Balances (in shares) at Dec. 31, 2012	2,950,000	36,443,000