Condensed Consolidated Statements of Equity (Unaudited) (USD $) In Thousands, except Share data, unless otherwise specified	Total USD ($)	Common Stock USD ($)	Additional Paid-In Capital USD ($)	Cumulative Dividends in Excess of Earnings USD ($)	Total Stockholders’ Equity USD ($)	Noncontrolling Interest USD ($)	Class A Common Stock	Class B Common Stock
Beginning balance at Dec. 31, 2011	$ 1,567,340	$ 2,284	$ 2,032,305	$ (467,249)	$ 1,567,340	$ 0
Beginning balance, shares at Dec. 31, 2011		228,491,000					0	0
Increase (Decrease) in Stockholders' Equity
Share-based award transactions, net (in shares)		626,000					0	0
Share-based award transactions, net	7,647	6	7,641	0	7,647	0
Issuance of common stock under the DRIP (in shares)		3,362,000					0	0
Issuance of common stock under the DRIP	31,915	33	31,882	0	31,915	0
Repurchase and cancellation of common stock (in shares)		(3,070,000)					(46,000)	(139,000)
Repurchase and cancellation of common stock	(31,935)	(32)	(31,903)	0	(31,935)	0
Conversion (in shares)		(229,409,000)					57,425,000	171,984,000
Dividends	(80,326)	0	0	(80,326)	(80,326)	0
Net income (loss)	(19,636)	0	0	(19,636)	(19,636)	0
Ending balance at Jun. 30, 2012	1,475,005	2,291	2,039,925	(567,211)	1,475,005	0
Ending balance, shares at Jun. 30, 2012		0					57,379,000	171,845,000
Beginning balance at Dec. 31, 2012	1,264,595	2,147	1,885,836	(633,717)	1,254,266	10,329
Beginning balance, shares at Dec. 31, 2012		0					100,086,000	114,566,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)		0					11,043,000	0
Issuance of common stock	124,397	111	124,286	0	124,397	0
Share-based award transactions, net (in shares)		0					411,000	0
Share-based award transactions, net	4,663	4	1,482	0	1,486	3,177
Issuance of common stock under the DRIP	0
Repurchase and cancellation of common stock (in shares)		0					(27,000)	0
Repurchase and cancellation of common stock	(272)	(1)	(271)	0	(272)	0
Conversion (in shares)							57,283,000	(57,283,000)
Dividends	(65,339)	0	0	(64,735)	(64,735)	(604)
Net income (loss)	15,567	0	0	15,376	15,376	191
Ending balance at Jun. 30, 2013	$ 1,343,611	$ 2,261	$ 2,011,333	$ (683,076)	$ 1,330,518	$ 13,093
Ending balance, shares at Jun. 30, 2013		0					168,796,000	57,283,000