Stockholders' Equity of the Company Stockholders' Equity of the Company (Details) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012		Apr. 16, 2012	Dec. 31, 2011
Accrued dividend and distributions
Accrued dividends and distributions	28,924			22,692
Summary of shares and units
Common stock	74,926,981	[1]		58,819,717	[1]
Noncontrolling common units	1,826,503			1,718,131
Common stockholders and noncontrolling unitholders [Member]
Accrued dividend and distributions
Accrued dividends and distributions	27,230			21,483
Common Stock [Member]
Accrued dividend and distributions
Accrued dividends and distributions	26,224			20,587
Capital Units [Member]
Accrued dividend and distributions
Accrued dividends and distributions	639			601
Preferred Stock [Member]
Accrued dividend and distributions
Accrued dividends and distributions	1,694			1,209
Series E Cumulative Redeemable Preferred Stock [Member]
Summary of shares and units
Preferred stock (in shares)			1,610,000	1,610,000
Series F Cumulative Redeemable Preferred Stock [Member]
Summary of shares and units
Preferred stock (in shares)			3,450,000	3,450,000
Series G Cumulative Redeemable Preferred Stock [Member]
Summary of shares and units
Preferred stock (in shares)	4,000,000
Series H Cumulative Redeemable Preferred Stock [Member]
Summary of shares and units
Preferred stock (in shares)	4,000,000
Restricted Stock Units (RSUs) [Member]
Accrued dividend and distributions
Accrued dividends and distributions	367	[2]		295	[2]
Time-Based Restricted Stock Units (RSUs) [Member]
Summary of shares and units
RSUs	1,048,863	[3]		842,675	[3]

[1] The amount includes nonvested shares.

[2] The amount includes the value of the dividend equivalents that will be paid with additional fully-vested RSUs (see Note 12)

[3] The amount includes nonvested RSUs.