Goodwill and Other Intangible Assets (Intangible Assets Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 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		$ 1,000,000
Net, intangible asset not subject to amortization	64,000,000		64,000,000		67,000,000
Gross carrying amount of capitalized software	1,200,000,000		1,200,000,000		1,200,000,000
Capitalized computer software, net	360,000,000		360,000,000		355,000,000
Capitalized computer software, development stage costs	42,000,000		$ 42,000,000
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		$ 0
Amortization expense				$ 2,000,000
Capitalized Internal Use Software [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired finite-lived intangible asset, residual value	0		0
Amortization expense	30,000,000	$ 35,000,000	91,000,000	$ 105,000,000
Amortization expense for remainder 2019	30,000,000		30,000,000
Amortization expense for 2020	119,000,000		119,000,000
Amortization expense for 2021	95,000,000		95,000,000
Amortization expense for 2022	58,000,000		58,000,000
Amortization expense for 2023	29,000,000		29,000,000
Amortization expense for 2024	20,000,000		20,000,000
Amortization expense thereafter	9,000,000		$ 9,000,000
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		$ 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	1,000,000
Amortization expense for remainder 2019	1,000,000		1,000,000
Amortization expense for 2020	0		0
Amortization expense for 2021	0		0
Amortization expense for 2022	$ 0		$ 0
Maximum [Member] | Capitalized Internal Use Software, Significant System Conversions [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period			10 years