Fair Value - Fair Value Measurements, Recurring and Nonrecurring (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021	Sep. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	$ 143,963	$ 130,930	$ 143,963
Trading	57,729	23,711	57,729
Equity method investments	20	13	$ 20
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	91,901	104,591
Equity investments at fair value		130,930
Total investments	201,712	154,654
Derivatives - assets:	4,581	690
Derivatives - liabilities:	120	887
Fair Value, Measurements, Recurring | Total return swaps - commodities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	75	481
Derivatives - liabilities:	116	17
Fair Value, Measurements, Recurring | Total return swaps - equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	3,067
Derivatives - liabilities:		867
Fair Value, Measurements, Recurring | Forward contracts - foreign exchange
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	1,439	209
Derivatives - liabilities:	4	3
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	91,901	104,591
Equity investments at fair value	129,087	128,855
Total investments	129,087	128,855
Derivatives - assets:	0	0
Derivatives - liabilities:	0	0
Fair Value, Measurements, Recurring | Level 1 | Total return swaps - commodities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	0
Fair Value, Measurements, Recurring | Level 1 | Forward contracts - foreign exchange
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - liabilities:	0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	779	116
Total investments	58,508	23,827
Derivatives - assets:	4,581	690
Derivatives - liabilities:	120	887
Fair Value, Measurements, Recurring | Level 2 | Total return swaps - commodities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	75	481
Derivatives - liabilities:	116	17
Fair Value, Measurements, Recurring | Level 2 | Total return swaps - equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	3,067
Derivatives - liabilities:		867
Fair Value, Measurements, Recurring | Level 2 | Forward contracts - foreign exchange
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - assets:	1,439	209
Derivatives - liabilities:	4	3
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments	12,610
Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	1,487	1,959
Total investments	1,507	1,972
Common stocks | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	128,440	126,417
Common stocks | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	127,672	126,301
Common stocks | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	768	116
Common stocks | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Company-sponsored funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	191
Company-sponsored funds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	191	103
Company-sponsored funds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Company-sponsored funds | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Limited partnership interests | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	13,967	1,816
Limited partnership interests | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0	0
Limited partnership interests | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Limited partnership interests | Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	12,610
Limited partnership interests | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	1,357	1,816
Master limited partnership interests | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	410	986
Master limited partnership interests | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	410	986
Preferred securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	825	1,465
Preferred securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	814	1,465
Preferred securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	11	0
Preferred securities | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Other | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	130	246
Other | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Other | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	0
Other | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity investments at fair value	130	143
Fixed income | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading		23,711
Fixed income | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	0
Fixed income | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	57,729	23,711
Fixed income | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading	$ 0	0
Equity method investments | Cohen & Steers Global Realty Partners III-TE, L.P.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment, ownership percentage	0.20%
Equity method investments | Cohen & Steers Global Listed Infrastructure Fund L.P.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investment, ownership percentage	0.01%
Equity method investments | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments		13
Equity method investments | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	$ 0	0
Equity method investments | Fair Value, Measurements, Recurring | Investments Measured at NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity method investments	$ 20	$ 13