Fair Value - Recurring Fair Values and Level 3 Recurring Fair Value Measurements (Details) $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets—derivative assets	$ 26,919	$ 21,386
Loans receivable, fair value	1,588,427
Equity method investments	218,340	222,875
Other liabilities—derivative liabilities	84,271	127,531
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, fair value	0	0
Equity method investments	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, fair value	0	0
Equity method investments	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans receivable, fair value	1,588,427	1,557,850
Equity method investments	218,340	222,875
N-Star CDO bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
N-Star CDO bonds, available for sale	$ 54,474	54,859
Discounted cash flows | N-Star CDO bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
N-Star CDO bonds, available for sale		$ 54,859
Discount rate | N-Star CDO bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.249	0.223
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	$ 102,399	$ 138,586
Other assets—derivative assets	26,919	21,386
Other liabilities—derivative liabilities	84,271	127,531
Contingent consideration—THL Hotel Portfolio (Note 12)	6,630	9,330
Other liabilities—settlement liability	4,910
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	102,399	138,586
Other assets—derivative assets	0	0
Other liabilities—derivative liabilities	0	0
Contingent consideration—THL Hotel Portfolio (Note 12)	0	0
Other liabilities—settlement liability	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	0	0
Other assets—derivative assets	26,919	21,386
Other liabilities—derivative liabilities	84,271	127,531
Contingent consideration—THL Hotel Portfolio (Note 12)	0	0
Other liabilities—settlement liability	0
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	0	0
Other assets—derivative assets	0	0
Other liabilities—derivative liabilities	0	0
Contingent consideration—THL Hotel Portfolio (Note 12)		9,330
Other liabilities—settlement liability	4,910
Recurring | N-Star CDO bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
N-Star CDO bonds, available for sale	54,474	54,859
Recurring | N-Star CDO bonds | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
N-Star CDO bonds, available for sale	0	0
Recurring | N-Star CDO bonds | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
N-Star CDO bonds, available for sale	0	0
Recurring | N-Star CDO bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
N-Star CDO bonds, available for sale	54,474	54,859
Recurring | CMBS of consolidated fund
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
CMBS of consolidated fund	2,224	2,732
Recurring | CMBS of consolidated fund | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
CMBS of consolidated fund	0	0
Recurring | CMBS of consolidated fund | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
CMBS of consolidated fund	2,224	2,732
Recurring | CMBS of consolidated fund | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
CMBS of consolidated fund	0	0
Loans receivable | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	1,568,302
Loans receivable | Transaction Price | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	$ 20,125
Loans receivable | Discount rate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.123
Private funds | NAV | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	$ 4,616	5,391
Other investment ventures | Discounted cash flows | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	17,870	18,574
Other investment ventures | Transaction Price | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	170,854	173,910
Other investment ventures | Multiple | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, fair value	$ 25,000	$ 25,000
Measurement input (percent)	4.1	3.7
Other investment ventures | Discount rate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.120	0.101
Minimum | Discount rate | N-Star CDO bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.182	0.168
Minimum | Loans receivable | Discount rate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.072
Minimum | Other investment ventures | Discount rate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.051	0.051
Maximum | Discount rate | N-Star CDO bonds | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.650	0.650
Maximum | Loans receivable | Discount rate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.255
Maximum | Other investment ventures | Discount rate | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input (percent)	0.165	0.158
THL Hotel Portfolio | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration—THL Hotel Portfolio (Note 12)	$ 6,630