Income Taxes - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, percent	26.50%		31.60%
Effective income tax rate reconciliation, including discrete items, percent	28.10%		33.50%
Discrete income tax expense	$ 2		$ 1
Tax Cuts And Jobs Act of 2017, incomplete accounting, provisional income tax expense (benefit)		$ 272