Selected Quarterly Financial Data - Additional information (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Impairment charges	$ 1,000,000	$ 4,500,000		$ 3,400,000		$ 6,300,000		$ 3,600,000
Cash reimbursement received by the Company for operating expenses			1,900,000
Loss on extinguishment of debt							(29,900,000)			29,638,000
Loss on extinguishment of debt, discontinued operations							300,000
Gains on sale of real estate	$ 9,300,000				$ 2,700,000	$ 20,200,000	$ 1,800,000		$ 9,283,000	$ 24,718,000	$ 10,874,000