Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Interest Expense [Abstract]
Interest expense before capitalization	$ 431	$ 452	$ 431
Capitalized interest	(19)	(24)	(39)
Interest expense	412	428	392
Interest paid, net	$ 445	419	$ 353
Interest recovered on the settlement of tax claims		$ 6