Related Party Transactions and Arrangements - Amount Contractually Due and Forgiven (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Payable to related party	$ 4,824		$ 4,824		$ 3,229
Affiliated Entity
Related Party Transaction [Line Items]
Total expenses from transactions with related party	9,802	$ 6,709	25,923	$ 18,123
Payable to related party	4,824		4,824		3,229
Affiliated Entity | Acquisition expenses | Nonrecurring Fees
Related Party Transaction [Line Items]
Total expenses from transactions with related party	180	173	698	289
Payable to related party	1		1		1
Affiliated Entity | Administrative services expenses | Nonrecurring Fees
Related Party Transaction [Line Items]
Total expenses from transactions with related party	4,564	3,501	12,083	9,822
Payable to related party	1,922		1,922		1,224
Affiliated Entity | Asset management and subordinated performance fee | Nonrecurring Fees
Related Party Transaction [Line Items]
Total expenses from transactions with related party	4,468	2,720	11,917	7,227
Payable to related party	2,671		2,671		1,072
Affiliated Entity | Other related party expenses | Nonrecurring Fees
Related Party Transaction [Line Items]
Total expenses from transactions with related party	590	315	1,225	785
Payable to related party	230		230		$ 932
Affiliated Entity | Acquisition fees and expenses, including amount capitalized | Nonrecurring Fees
Related Party Transaction [Line Items]
Total expenses from transactions with related party	1,600	2,400	5,400	6,600
Affiliated Entity | Acquisition fees and expenses, amount capitalized | Nonrecurring Fees
Related Party Transaction [Line Items]
Total expenses from transactions with related party	$ 1,400	$ 2,200	$ 4,700	$ 6,300