Income Taxes - Operating Loss Carryforward and Tax Credit Carryforward (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Operating Loss Carryforwards [Line Items]
Increase in valuation allowance to adjust tax benefit of certain state deferred tax assets and net operating loss carryforwards	$ 13
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	19
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 182