Income Taxes (Components of deferred tax assets and liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Reserves and allowances	$ 111	$ 126
Debt cancellation and other	8	11
Net operating loss and credit carryforwards	371	435
Operating lease assets	182
Total deferred tax assets	672	572
Valuation allowance	(43)	(46)
Total net deferred tax assets	629	526
Property and equipment	(2,135)	(1,976)
Operating lease liabilities	(182)
Intangibles	(199)	(237)
Total deferred tax liability	(2,516)	(2,213)
Total net deferred tax liability	$ (1,887)	$ (1,687)