Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Effective tax rate on income from continuing operations (as a percent)	15.40%	14.40%	15.80%	14.90%
Benefits Tax Planning and Completion of Audits		$ 20		$ 20
Valuation allowance	$ 22		$ 22		$ 20
Gross unrecognized tax benefits	107		107		92
Unrecognized tax benefits net of federal tax benefits that would affect the effective tax rate	71		71		70
Increase (decrease) in interest and penalties	1	$ 0	1	$ 1
Payable related to accrued interest and penalties	11		11		$ 10
Minimum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in gross unrecognized tax benefits due to resolution of audits and statute expirations	50		50
Maximum [Member]
Operating Loss Carryforwards [Line Items]
Decrease in gross unrecognized tax benefits due to resolution of audits and statute expirations	60		60
State and Local [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses	$ 21		$ 21