Consolidation - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Assets
Cash equivalents	$ 157,635	$ 287,126
Total assets measured at fair value	287,427	374,279
Liabilities
Total liabilities measured at fair value	54,910	78,100
Level 1
Assets
Cash equivalents	157,635	287,126
Total assets measured at fair value	263,088	374,279
Liabilities
Total liabilities measured at fair value	0	0
Level 2
Assets
Cash equivalents	0	0
Total assets measured at fair value	0	0
Liabilities
Total liabilities measured at fair value	0	0
Level 3
Assets
Cash equivalents	0	0
Total assets measured at fair value	24,339	0
Liabilities
Total liabilities measured at fair value	54,910	78,100
Fair Value, Measurements, Recurring | Consolidated Investment Products
Assets
Cash equivalents	208,056	249,003
Total assets measured at fair value	2,277,271	2,439,116
Liabilities
Notes payable	1,943,949	2,083,314
Short sales	489	414
Total liabilities measured at fair value	1,944,438	2,083,728
Fair Value, Measurements, Recurring | Debt investments | Consolidated Investment Products
Assets
Investments	2,038,674	2,161,571
Fair Value, Measurements, Recurring | Equity investments | Consolidated Investment Products
Assets
Investments	30,541	28,542
Fair Value, Measurements, Recurring | Level 1 | Consolidated Investment Products
Assets
Cash equivalents	208,056	249,003
Total assets measured at fair value	236,984	274,249
Liabilities
Notes payable	0	0
Short sales	489	414
Total liabilities measured at fair value	489	414
Fair Value, Measurements, Recurring | Level 1 | Debt investments | Consolidated Investment Products
Assets
Investments	167	243
Fair Value, Measurements, Recurring | Level 1 | Equity investments | Consolidated Investment Products
Assets
Investments	28,761	25,003
Fair Value, Measurements, Recurring | Level 2 | Consolidated Investment Products
Assets
Cash equivalents	0	0
Total assets measured at fair value	1,977,005	2,121,286
Liabilities
Notes payable	1,943,949	2,083,314
Short sales	0	0
Total liabilities measured at fair value	1,943,949	2,083,314
Fair Value, Measurements, Recurring | Level 2 | Debt investments | Consolidated Investment Products
Assets
Investments	1,976,568	2,119,082
Fair Value, Measurements, Recurring | Level 2 | Equity investments | Consolidated Investment Products
Assets
Investments	437	2,204
Fair Value, Measurements, Recurring | Level 3 | Consolidated Investment Products
Assets
Cash equivalents	0	0
Total assets measured at fair value	63,282	43,581
Liabilities
Notes payable	0	0
Short sales	0	0
Total liabilities measured at fair value	0	0
Fair Value, Measurements, Recurring | Level 3 | Debt investments | Consolidated Investment Products
Assets
Investments	61,939	42,246
Fair Value, Measurements, Recurring | Level 3 | Equity investments | Consolidated Investment Products
Assets
Investments	$ 1,343	$ 1,335