Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Percent	22.70%	24.50%
Corporate Federal Income Tax Rate	21.00%	35.00%
Current State and Local Tax Expense (Benefit)		$ 14
Deferred Tax Assets, Net	$ 123		$ 93
Operating Loss Carryforwards, Valuation Allowance	$ 4