v3.26.1
Earnings Per Share - Computation of basic and diluted net income per share (Details) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Earnings Per Share [Abstract]          
Net income attributable to APAM $ 80,828 $ 67,555 $ 138,869 $ 128,694  
Less: Allocation to participating securities 6,953 5,974 13,051 11,886  
Net income available to common stockholders $ 73,875 $ 61,581 $ 125,818 $ 116,808  
Basic weighted average shares outstanding (in shares) 66,355,850 65,645,108 66,241,557 65,509,947  
Dilutive effect of nonparticipating share-based awards (in shares) 0 0 0 0  
Diluted weighted average shares outstanding (in shares) 66,355,850 65,645,108 66,241,557 65,509,947  
Earnings per share - Basic (in dollars per share) $ 1.11 $ 0.94 $ 1.90 $ 1.78  
Earnings per share - Diluted (in dollars per share) $ 1.11 $ 0.94 $ 1.90 $ 1.78  
Performance Shares          
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]          
Unvested - Number of awards (in shares) 152,207   152,207   152,207