Concentration of Credit Risk (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk (Line Items)
Revenues	$ 109,847	$ 104,965	$ 101,792	$ 94,226	$ 93,906	$ 98,331	$ 94,410	$ 94,464	$ 410,830	$ 381,111
Cohen & Steers Realty Shares, Inc. (CSR) | Customer Concentration Risk
Concentration Risk (Line Items)
Percent of total revenue									9.00%	9.90%	11.40%
Cohen & Steers Realty Shares, Inc. (CSR) | Investment advisory and administration fees | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 32,884	$ 33,827	$ 38,392
Cohen & Steers Realty Shares, Inc. (CSR) | Distribution and Shareholder Service [Member] | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 4,079	$ 4,032	$ 4,602
Cohen & Steers Preferred Securities and Income Fund, Inc. (CPX) | Customer Concentration Risk
Concentration Risk (Line Items)
Percent of total revenue									16.90%	17.50%	18.00%
Cohen & Steers Preferred Securities and Income Fund, Inc. (CPX) | Investment advisory and administration fees | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 56,638	$ 53,059	$ 53,594
Cohen & Steers Preferred Securities and Income Fund, Inc. (CPX) | Distribution and Shareholder Service [Member] | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 12,753	$ 13,525	$ 14,744
Cohen & Steers Real Estate Securities Fund, Inc. (CSI) | Customer Concentration Risk
Concentration Risk (Line Items)
Percent of total revenue									12.20%	10.10%	9.20%
Cohen & Steers Real Estate Securities Fund, Inc. (CSI) | Investment advisory and administration fees | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 41,971	$ 31,759	$ 27,033
Cohen & Steers Real Estate Securities Fund, Inc. (CSI) | Distribution and Shareholder Service [Member] | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 8,128	$ 6,841	$ 7,662
Daiwa Asset Management | Customer Concentration Risk
Concentration Risk (Line Items)
Percent of total revenue									7.80%	8.80%	10.80%
Daiwa Asset Management | Investment advisory and administration fees | Customer Concentration Risk
Concentration Risk (Line Items)
Revenues									$ 31,957	$ 33,454	$ 40,791