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Fair Value of Assets and Liabilities - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair value of assets and liabilities
Loss on asset impairment		$ 0	$ 1,300	$ 0	$ 19,714	$ 43,736
Real estate properties, net		1,503,776			$ 1,503,776		$ 2,101,635
Total rents \| Credit concentration
Fair value of assets and liabilities
Concentration risk, percent					8.00%
Real Estate Held-for-sale
Fair value of assets and liabilities
Loss on asset impairment	$ 18,400
Real Estate Held-for-sale \| Level 2 \| Market Approach Valuation Technique
Fair value of assets and liabilities
Assets, fair value		80,600	23,300		$ 80,600
Fair Value, Measurements, Nonrecurring \| Disposition Plan \| Carrying Amount
Fair value of assets and liabilities
Real estate properties, net		$ 99,000	$ 24,600		$ 99,000