Income Taxes (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Abstract]
Adjustment of deferred tax balances	$ 3	$ 23	$ 7
Domestic production activities deduction		14
Federal research and development credits	5	5	5
Reversal of reserves for uncertain tax postions			2
Tax reserve adjustment		11
Settlement of 2010 IRS audit			5
Non-deductible transaction costs		2	$ 3
Effect of expiration of statute of limitations during next twelve months	1
Federal net operating loss carryforward	244
State tax operating loss carryforward	4,100
Gross tax liability for tax positions that may not be sustained under a more likely than not threshold	20
Additional interest recognized on tax liability	1
Accrued interest on tax liability	$ 1	$ 1