Summary of Significant Accounting Policies - Variable Interest Entity Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets
Net investments in properties	$ 5,511,706	$ 5,826,544
Net investment in direct financing leases	684,059	756,353
In-place lease and tenant relationship intangible assets, net	826,113	902,848
Above-market rent intangible assets, net	421,456	475,072
Total assets	8,453,954	8,742,089
Liabilities
Non-recourse debt, net	1,706,921	2,269,421
Total liabilities	5,027,849	5,165,717
Variable Interest Entity
Assets
Net investments in properties	786,379	890,454
Net investment in direct financing leases	60,294	61,454
In-place lease and tenant relationship intangible assets, net	182,177	214,924
Above-market rent intangible assets, net	71,852	80,901
Total assets	1,150,093	1,297,276
Liabilities
Non-recourse debt, net	406,574	439,285
Total liabilities	$ 548,659	$ 590,596