Consolidated Statement of Changes in Stockholders' Equity and Noncontrolling Interests (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Redeemable Noncontrolling Interests	Series D Preferred Stock	Series D Preferred Stock Preferred Stock	Series E Cumulative Redeemable Preferred Stock	Series E Cumulative Redeemable Preferred Stock Preferred Stock
Beginning balance at Dec. 31, 2013	$ 14,444						$ 14,444
Beginning balance at Dec. 31, 2013	3,964,497	712	3,572,281	0	(36,204)	47,708			250,000		130,000
Beginning balance, common shares at Dec. 31, 2013		71,172,197
Increase (Decrease) in Stockholders' Equity
Net Income	112,011			108,966		3,045
Total other comprehensive income (loss)	7,493				7,493	0
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	19,410					19,410
Distributions to noncontrolling interests	(2,594)					(2,594)
Issuances pursuant to stock plan (in shares)		199,628
Issuances pursuant to stock plan	15,033	2	15,031
Dividends declared on common stock	(153,669)			(153,669)
Dividends declared on preferred stock	(19,414)			(19,414)
Distributions in excess of earnings			(64,117)	64,117
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income							797
Total other comprehensive income (loss)							0
Distributions to noncontrolling interests							(893)
Ending balance at Sep. 30, 2014	14,348						14,348
Ending balance at Sep. 30, 2014	3,942,767	714	3,523,195	0	(28,711)	67,569			250,000		130,000
Ending balance, common shares at Sep. 30, 2014		71,371,825
Beginning balance at Jun. 30, 2014
Increase (Decrease) in Stockholders' Equity
Total other comprehensive income (loss)	(12,466)
Dividends declared on common stock	(51,800)
Dividends declared on preferred stock								(4,400)		(2,100)
Ending balance at Sep. 30, 2014	14,348
Ending balance at Sep. 30, 2014	$ 3,942,767								$ 250,000		$ 130,000