Summary of Significant Accounting Policies (Details 8) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 BuyEfficient, LLC	Jan. 31, 2011 BuyEfficient, LLC
Investments in unconsolidated joint ventures
Ownership interest acquired (as a percent)												50.00%	50.00%
Earnings Per Share
Two-class method assumption, percentage of net income distributed as dividends to each class of stock									100.00%
Numerator:
Net income	$ 11,114,000	$ 39,556,000	$ 11,855,000	$ (12,968,000)	$ 7,588,000	$ (16,553,000)	$ 38,929,000	$ 51,335,000	$ 49,557,000	$ 81,299,000	$ 38,542,000
Income from consolidated joint venture attributable to non-controlling interest									(1,761,000)	(312,000)
Distributions to non-controlling interest									(31,000)	(30,000)
Preferred stock dividends and accretion									(29,748,000)	(27,321,000)	(20,652,000)
Undistributed income allocated to unvested restricted stock compensation									(203,000)	(636,000)	(102,000)
INCOME AVAILABLE TO COMMON STOCKHOLDERS									$ 17,814,000	$ 53,000,000	$ 17,788,000
Denominator:
Weighted average basic and diluted common shares outstanding									127,027	117,206	99,709
Basic and diluted earnings available to common stockholders per common share	$ 0.03	$ 0.23	$ 0.03	$ (0.18)	$ 0.00	$ (0.20)	$ 0.27	$ 0.39	$ 0.14	$ 0.45	$ 0.18
Segment Reporting
Number of operating segments									1