Contingencies - Schedule of Estimated Indirect Foreign Exchange Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Commitments and Contingencies Disclosure [Abstract]
Estimated indirect foreign exchange revenue	$ 280	$ 246	$ 285	$ 248	$ 331	$ 336	$ 369	$ 462