Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Tax And Effective Tax Rate [Abstract]
Income tax provision	$ 76	$ 67
Effective tax rate	15.00%	19.40%
Tax Year 2017 [Member]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%
Tax Year 2018 [Domain]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%
Income Tax And Effective Tax Rate [Abstract]
Limit on deductibility of interest expense	30.00%
Remeasurement of Deferreds [Member]
Income Tax And Effective Tax Rate [Abstract]
Income tax provision	$ 16