Business, Basis of Presentation and Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from contract with customer excluding assessed tax percentage	21.20%	23.40%	19.70%
Accounting Standards Update 2014-09
Disaggregation of Revenue [Line Items]
Accounts Receivable, after Allowance for Credit Loss	$ 107	$ 88
Recordkeeping & administration
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	514	423	$ 405
Distribution & shareholder servicing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 180	$ 158	$ 82