Consolidation - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Assets
Cash equivalents	$ 307,277,000	$ 207,101,000
Total assets measured at fair value	400,933,000	257,703,000
Liabilities
Derivatives	0
Total liabilities measured at fair value	88,400,000
Level 1
Assets
Cash equivalents	307,277,000	207,101,000
Total assets measured at fair value	400,933,000	257,700,000
Liabilities
Total liabilities measured at fair value	0
Level 2
Assets
Cash equivalents	0	0
Total assets measured at fair value	0	3,000
Liabilities
Total liabilities measured at fair value	0
Level 3
Assets
Cash equivalents	0	0
Total assets measured at fair value	0	0
Liabilities
Total liabilities measured at fair value	88,400,000
Fair Value, Measurements, Recurring | Consolidated Investment Products
Assets
Cash equivalents	205,192,000	82,295,000
Total assets measured at fair value	2,345,430,000	2,416,944,000
Liabilities
Notes payable	2,033,617,000	2,190,445,000
Derivatives		1,471,000
Short sales	515,000	520,000
Total liabilities measured at fair value	2,034,132,000	2,192,436,000
Fair Value, Measurements, Recurring | Debt investments | Consolidated Investment Products
Assets
Investments	2,110,704,000	2,289,426,000
Fair Value, Measurements, Recurring | Equity Securities [Member] | Consolidated Investment Products
Assets
Investments	29,534,000	43,138,000
Derivatives		2,085,000
Fair Value, Measurements, Recurring | Level 1 | Consolidated Investment Products
Assets
Cash equivalents	205,192,000	82,295,000
Total assets measured at fair value	231,576,000	138,480,000
Liabilities
Notes payable	0	0
Derivatives		714,000
Short sales	515,000	520,000
Total liabilities measured at fair value	515,000	1,234,000
Fair Value, Measurements, Recurring | Level 1 | Debt investments | Consolidated Investment Products
Assets
Investments	273,000	16,859,000
Fair Value, Measurements, Recurring | Level 1 | Equity Securities [Member] | Consolidated Investment Products
Assets
Investments	26,111,000	38,468,000
Derivatives		858,000
Fair Value, Measurements, Recurring | Level 2 | Consolidated Investment Products
Assets
Cash equivalents	0	0
Total assets measured at fair value	2,110,697,000	2,224,282,000
Liabilities
Notes payable	2,033,617,000	2,190,445,000
Derivatives		757,000
Short sales	0	0
Total liabilities measured at fair value	2,033,617,000	2,191,202,000
Fair Value, Measurements, Recurring | Level 2 | Debt investments | Consolidated Investment Products
Assets
Investments	2,107,736,000	2,219,199,000
Fair Value, Measurements, Recurring | Level 2 | Equity Securities [Member] | Consolidated Investment Products
Assets
Investments	2,961,000	3,856,000
Derivatives		1,227,000
Fair Value, Measurements, Recurring | Level 3 | Consolidated Investment Products
Assets
Cash equivalents	0	0
Total assets measured at fair value	3,157,000	54,182,000
Liabilities
Notes payable	0	0
Derivatives		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	2,695,000	53,368,000
Fair Value, Measurements, Recurring | Level 3 | Equity Securities [Member] | Consolidated Investment Products
Assets
Investments	$ 462,000	814,000
Derivatives		$ 0