Earnings (Loss) Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Numerator for earnings (loss) per share calculation:
Net income attributable to GCM Grosvenor Inc., basic	$ 7,605	$ 656	$ 12,331	$ 3,203
Net income (loss) attributable common stockholders, diluted	$ 25,422	$ (3,577)	$ 38,959	$ (6,989)
Denominator for earnings per share calculation:
Weighted-average shares, basic (in shares)	45,118,448	44,563,266	44,857,546	43,330,664
Exchange of Partnership units (in shares)	144,235,246	144,235,246	144,235,246	144,235,246
Assumed vesting of RSUs - incremental shares under the treasury stock method (in shares)	444	0	418,753	0
Weighted-average shares, diluted (in shares)	189,354,138	188,798,512	189,511,545	189,128,826
Basic EPS
Net income attributable to common stockholders, basic	$ 7,605	$ 656	$ 12,331	$ 3,203
Weighted-average shares, basic (in shares)	45,118,448	44,563,266	44,857,546	43,330,664
Net income per share attributable to common stockholders, basic (in dollars per share)	$ 0.17	$ 0.01	$ 0.27	$ 0.07
Diluted EPS
Net income (loss) attributable common stockholders, diluted	$ 25,422	$ (3,577)	$ 38,959	$ (6,989)
Weighted-average shares, diluted (in shares)	189,354,138	188,798,512	189,511,545	189,128,826
Net income (loss) per share attributable to common stockholders, diluted (in dollars per share)	$ 0.13	$ (0.02)	$ 0.21	$ (0.04)
Private warrants
Numerator for earnings (loss) per share calculation:
Exercise of warrants	$ 0	$ 0	$ 0	$ (412)
Denominator for earnings per share calculation:
Exercise of warrants - incremental shares under the treasury stock method (in shares)	0	0	0	180,124
Public warrants
Numerator for earnings (loss) per share calculation:
Exercise of warrants	$ 0	$ 0	$ 0	$ (1,179)
Denominator for earnings per share calculation:
Exercise of warrants - incremental shares under the treasury stock method (in shares)	0	0	0	1,382,792
Partnership Units
Numerator for earnings (loss) per share calculation:
Exercise of warrants	$ 17,817	$ (4,233)	$ 26,628	$ (8,601)