Goodwill and Other Intangible Assets (Intangible Assets Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired during the year	$ 0
Finite-lived intangible assets, gross	1,000,000		$ 1,000,000
Net, intangible asset not subject to amortization	66,000,000		67,000,000
Gross carrying amount of capitalized software	1,200,000,000		1,200,000,000
Capitalized computer software, net	339,000,000		355,000,000
Capitalized computer software, development stage costs	$ 52,000,000
Finite-Lived Intangible Assets, Except Capitalized Internal-Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	2 years
Acquired finite-lived intangible asset, residual value	$ 0
Capitalized Internal Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible asset, residual value	0
Amortization expense	30,000,000	$ 36,000,000
Amortization expense for remainder 2019	87,000,000
Amortization expense for 2020	107,000,000
Amortization expense for 2021	58,000,000
Amortization expense for 2022	36,000,000
Amortization expense for 2023	25,000,000
Amortization expense for 2024	14,000,000
Amortization expense thereafter	$ 12,000,000
Capitalized Internal Use Software, Except Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	3 years
Minimum [Member] | Capitalized Internal Use Software, Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	8 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived intangible assets, net	$ 1,000,000		$ 1,000,000
Maximum [Member] | Finite-Lived Intangible Assets, Except Capitalized Internal-Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense	1,000,000	$ 1,000,000
Amortization expense for remainder 2019	1,000,000
Amortization expense for 2020	1,000,000
Amortization expense for 2021	1,000,000
Amortization expense for 2022	$ 1,000,000
Maximum [Member] | Capitalized Internal Use Software, Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	10 years