Fee Income - Earned (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fee income
Related Party Transaction [Line Items]
Revenue from contract with customer	$ 151,821	$ 220,789	$ 67,731
Fee income | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from contract with customer	150,596	184,914	67,731
Base management fees ($137,762, $165,436 and $63,212 from affiliates, respectively)
Related Party Transaction [Line Items]
Revenue from contract with customer	138,784	183,838	63,212
Base management fees ($137,762, $165,436 and $63,212 from affiliates, respectively) | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from contract with customer	137,762	165,436	63,212
Asset management fees—from affiliates | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from contract with customer	2,078	3,069	4,519
Acquisition and disposition fees—from affiliates | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from contract with customer	1,922	16,237	0
Incentive fees ($5,445, $172, $0 from affiliates, respectively)
Related Party Transaction [Line Items]
Revenue from contract with customer	5,445	1,043	0
Incentive fees ($5,445, $172, $0 from affiliates, respectively) | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from contract with customer	5,445	172	0
Other fee income ($3,389, $0 and $0 from affiliates, respectively)
Related Party Transaction [Line Items]
Revenue from contract with customer	3,592	16,602	0
Other fee income ($3,389, $0 and $0 from affiliates, respectively) | Affiliated Entity
Related Party Transaction [Line Items]
Revenue from contract with customer	3,389	0	0
Institutional funds | Fee income
Related Party Transaction [Line Items]
Revenue from contract with customer	56,002	60,988	67,731
Non Traded REIT | Fee income
Related Party Transaction [Line Items]
Revenue from contract with customer	29,597	88,081	0
Public companies (Colony Credit, NRE) | Fee income
Related Party Transaction [Line Items]
Revenue from contract with customer	65,258	14,003	0
Broker-dealer, Townsend and other clients | Fee income
Related Party Transaction [Line Items]
Revenue from contract with customer	$ 964	$ 57,717	$ 0