Investments in Unconsolidated Joint Ventures - Combined Condensed Balance Sheets of Unconsolidated Joint Ventures (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Properties, net	$ 3,288,060	$ 2,967,878
Other assets	253,070	208,726
Total assets	3,541,130	3,176,604
Liabilities and partners' capital:
Mortgage notes payable	1,818,390	2,038,379
Other liabilities	180,809	195,766
Company's capital	786,825	489,349
Outside partners' capital	755,106	453,110
Total liabilities and partners' capital	3,541,130	3,176,604
Investments in unconsolidated joint ventures:
Company's capital	786,825	489,349
Basis adjustment	466,535	464,826
Investments in unconsolidated joint ventures	1,253,360	954,175
Assets—Investments in unconsolidated joint ventures	1,278,216	984,132
Liabilities—Distributions in excess of investments in unconsolidated joint ventures	$ (24,856)	$ (29,957)