Income Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Excess tax benefits from share-based compensation	$ 2	$ 8	$ 3
Deferred tax assets	16
Increase in deferred tax asset valuation allowance	7
Valuation allowance	16	9
Impact on effective tax rate if tax benefits are recognized	9	$ 7	$ 2
Liability for unrecognized tax benefits	2
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	315
Tax credit carryovers	$ 11