Other Revenues and Other Expenses Other Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 345	$ 337
Other revenues	439	494
Prepaid legal plans
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	101	86
Fee-based investment management
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	79	77
Recordkeeping and administrative services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	49	50
Administrative services-only contracts
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	56	53
Other revenue from service contracts from customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	60	71
Other Income
Disaggregation of Revenue [Line Items]
Other revenues	$ 94	$ 157