Summary of Significant Accounting Policies - Schedule of Adoption of ASU 2016-13 (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	$ 2,016,892	$ 2,000,837	$ 1,973,501		$ 2,201,350	$ 2,209,055	$ 2,663,118	$ 2,816,912	$ 2,845,202
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Retained Earnings (Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity	$ (1,181,747)	$ (1,186,754)	$ (959,695)		(819,738)	$ (809,344)	$ (397,398)	$ (234,145)	$ (193,327)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity					(23,186)
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings (Accumulated Deficit)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity				$ 23,186	$ (22,644)
Cumulative Effect, Period of Adoption, Adjustment | CECL reserve on Loans and preferred equity held for investment, net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity				21,093
Cumulative Effect, Period of Adoption, Adjustment | CECL reserve on Accrued and other liabilities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total equity				$ 2,093