Other Revenues and Other Expenses Other Revenues (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 324	$ 328	$ 661	$ 650
Other revenues	478	475	972	949
Prepaid legal plans
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	86	73	172	146
Fee-based investment management
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	69	74	146	145
Recordkeeping and administrative services
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	52	56	102	114
Administrative services-only contracts
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	53	53	106	109
Other revenue from service contracts from customers
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	64	72	135	136
Other Income
Disaggregation of Revenue [Line Items]
Other revenues	$ 154	$ 147	$ 311	$ 299