Employee Retirement Benefits - Net Periodic Income Cost Recognizedf for OCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Total	$ 42	$ 43	$ (97)
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service benefit (net of $3 tax expense)	0	4	0
Net gains (losses) (net of $27 and $29 tax benefit and $58 tax expense, respectively)	44	45	(91)
Amortization of prior service benefit	0	(1)	(2)
Total	(44)	(40)	93
Tax effects on components of net periodic income (cost) recognized in OCI [Abstract]
Prior service benefit (cost)	0	3	0
Net gains (losses)	$ (27)	$ (29)	$ 58