Business Combinations - Assets Acquired and Liabilities & Equity Assumed (Details) - USD ($) $ in Thousands	Feb. 01, 2021	Sep. 30, 2021	Dec. 31, 2020
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Goodwill		$ 315,366	$ 290,366
AllianzGI
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Total definite-lived intangible assets	$ 120,388
Goodwill	25,000
Total assets acquired	145,388
Open-end and closed-end fund investment contracts | AllianzGI
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Total definite-lived intangible assets	$ 101,447
Weighted Average Useful Life	13 years
Retail separate account investment contracts | AllianzGI
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Total definite-lived intangible assets	$ 17,000
Weighted Average Useful Life	6 years
Trade name | AllianzGI
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Total definite-lived intangible assets	$ 1,941
Weighted Average Useful Life	8 years