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	Class A Common Stock	Class B	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						41,000		12,000
Share-based award transactions, net	12,290	7	6,358	0	6,365	5,925
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)						(14,936,000)		(144,000)
Repurchase and cancellation of common stock	(185,278)	(181)	(185,097)	0	(185,278)	0
Conversion (in shares)		(229,409,000)						57,429,000		171,980,000
Dividends	(111,238)	0	0	(111,165)	(111,165)	(73)
Net income (loss)	(22,588)	0	0	(22,588)	(22,588)	0
Ending balance at Sep. 30, 2012	1,292,441	2,143	1,885,448	(601,002)	1,286,589	5,852
Ending balance, shares at Sep. 30, 2012		0						42,534,000		171,848,000
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					100,086,387	100,086,000	114,566,254	114,566,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock (in shares)		0						20,707,000		0
Issuance of common stock	228,306	207	228,099	0	228,306	0
Share-based award transactions, net (in shares)		0						427,000		(15,000)
Share-based award transactions, net	5,129	4	1,948	0	1,952	3,177
Issuance of common stock under the DRIP	0
Repurchase and cancellation of common stock (in shares)		0						(28,000)		0
Repurchase and cancellation of common stock	(287)	0	(287)	0	(287)	0
Conversion (in shares)								57,283,000		(57,283,000)
Dividends	(99,584)	0	0	(98,630)	(98,630)	(954)
Net income (loss)	20,552	0	0	20,199	20,199	353
Ending balance at Sep. 30, 2013	$ 1,418,711	$ 2,358	$ 2,115,596	$ (712,148)	$ 1,405,806	$ 12,905
Ending balance, shares at Sep. 30, 2013		0					178,475,080	178,475,000	57,268,109	57,268,000