Consolidated Statement of Changes in Stockholders' Equity and Noncontrolling Interests (Unaudited) - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income	Noncontrolling Interests	Redeemable Noncontrolling Interests	7.00% Series D Cumulative Convertible Preferred Stock	7.00% Series D Cumulative Convertible Preferred Stock Preferred Stock	7.00% Series D Cumulative Convertible Preferred Stock Additional Paid-In Capital	7.00% Series D Cumulative Convertible Preferred Stock Retained Earnings	6.45% Series E Cumulative Redeemable Preferred Stock	6.45% Series E Cumulative Redeemable Preferred Stock Preferred Stock	6.45% Series E Cumulative Redeemable Preferred Stock Additional Paid-In Capital	6.45% Series E Cumulative Redeemable Preferred Stock Retained Earnings
Beginning balance (shares) at Dec. 31, 2016		87,665,880
Beginning balance at Dec. 31, 2016	$ 5,370,971	$ 877	$ 4,672,650	$ 0	$ 5,355	$ 475,175			$ 86,914				$ 130,000
Increase (Decrease) in Stockholders' Equity
Net Income	47,328			41,711		5,617
Total other comprehensive income	16,109				16,105	4
Distributions to noncontrolling interests	(5,108)					(5,108)
Sale of and contributions from noncontrolling interests	6,888		0			6,888
Issuances of common stock (shares)		2,100,000
Issuances of common stock	217,759	$ 21	217,738
Issuances pursuant to stock plan (in shares)		118,373
Issuances pursuant to stock plan	8,718	$ 1	8,717
Repurchase/redemption of preferred stock								$ (17,934)	(12,528)	$ 391	$ (5,797)	$ (130,350)	(130,000)	$ 5,132	$ (5,482)
Dividends declared on common stock	(75,590)			(75,590)
Dividends declared on preferred stock	(3,784)			(3,784)				$ (1,300)				$ (2,100)
Distributions in excess of earnings	0		(48,942)	48,942
Ending balance (shares) at Mar. 31, 2017		89,884,253
Ending balance at Mar. 31, 2017	5,435,007	$ 899	$ 4,855,686	$ 0	$ 21,460	$ 482,576			$ 74,386				$ 0
Beginning balance at Dec. 31, 2016	11,307						$ 11,307
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income							227
Total other comprehensive income							0
Distributions to noncontrolling interests							(214)
Ending balance at Mar. 31, 2017	$ 11,320						$ 11,320