Other Revenues and Other Expenses Other Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 313	$ 329	$ 974	$ 979
Other revenues	419	479	1,391	1,428
Prepaid legal plans
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	87	74	259	220
Fee-based investment management
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	67	74	213	219
Recordkeeping and administrative services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	52	56	154	170
Administrative services-only contracts
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	53	53	159	162
Other revenue from service contracts from customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	54	72	189	208
Other Income
Disaggregation of Revenue [Line Items]
Other revenues	$ 106	$ 150	$ 417	$ 449