Summary of Significant Accounting Policies - Real Estate Lease Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Acquired real estate leases:
Capitalized above market lease values	$ 12,304	$ 34,587
Less: accumulated amortization	(9,236)	(30,039)
Capitalized above market lease values, net	3,068	4,548
Lease, Net
Lease origination value	551,141	642,158
Less: accumulated amortization	(267,696)	(308,831)
Lease origination value, net	283,445	333,327
Acquired real estate leases and other intangible assets, net	286,513	337,875
Assumed real estate lease obligations:
Capitalized below market lease values	128,991	134,225
Less: accumulated amortization	(61,161)	(57,520)
Assumed real estate lease obligations, net	$ 67,830	$ 76,705