Goodwill and Other Intangible Assets (Intangible Assets Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired during the year	$ 0
Finite-Lived Intangible Assets, Gross	18,000,000		$ 18,000,000
Finite-Lived Intangible Assets, Net	10,000,000		10,000,000
Indefinite-Lived Intangible Assets (Excluding Goodwill)	77,000,000		79,000,000
Capitalized Computer Software, Gross	1,200,000,000		1,200,000,000
Capitalized Computer Software, Net	404,000,000		$ 416,000,000
Capitalized Computer Software, Development Stage Costs	$ 37,000,000
Finite-Lived Intangible Assets, Except Capitalized Internal-Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	6 years
Acquired Finite-lived Intangible Asset, Residual Value	$ 0
Amortization expense	1,000,000	$ 2,000,000
Amortization expense for remainder 2018	2,000,000
Amortization expense for 2019	2,000,000
Amortization expense for 2020	1,000,000
Amortization expense for 2021	1,000,000
Amortization expense for 2022	1,000,000
Amortization expense for 2023	1,000,000
Amortization expense thereafter	2,000,000
Capitalized Internal Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Asset, Residual Value	0
Amortization expense	36,000,000	$ 49,000,000
Amortization expense for remainder 2018	114,000,000
Amortization expense for 2019	108,000,000
Amortization expense for 2020	74,000,000
Amortization expense for 2021	48,000,000
Amortization expense for 2022	33,000,000
Amortization expense for 2023	17,000,000
Amortization expense thereafter	$ 10,000,000
Capitalized Internal Use Software, Except Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	3 years
Minimum [Member] | Capitalized Internal Use Software, Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	8 years
Maximum [Member] | Capitalized Internal Use Software, Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Weighted-Average Useful Life	10 years