Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, percent	25.90%	26.50%
Effective income tax rate reconciliation, including discrete items, percent	27.20%	28.10%
Discrete income tax expense	$ 1	$ 2