Organization and Basis of Presentation - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2019
Ground Leases Disclosures [Abstract]
2019 (remainder of year)		$ 735
2020		1,373
2021		1,235
2022		1,136
2023		1,036
Thereafter		40,770
Total minimum payments		46,285
Imputed interest		(27,311)
Amortization		(357)
Lease liabilities	$ 0	18,617
Deferred rent		(686)
Right of use asset	0	17,931
Leases, Operating [Abstract]
2019	1,512
2020	1,356
2021	1,205
2022	1,082
2023	981
Thereafter	40,799
Future minimum payments due	46,935
Leasing expense	$ 1,500
Operating Leases Receivable
Remainder of 2019		257,238
2020		494,928
2021		439,299
2022		369,584
2023		300,516
2024		242,833
Thereafter		863,024
Total		$ 2,967,422