Employee Benefit Plan - Amounts Included in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total benefits included in accumulated other comprehensive income, before tax	$ (107)	$ (134)
Total benefits included in accumulated other comprehensive income, after tax	(97)	(110)
Total expected amortization from accumulated other comprehensive income for the year ended December 31, 2013	5
Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service credits before tax	15	19
Actuarial gain (losses), net before tax	(131)	(164)
Prior service credits after tax	14	15
Actuarial gain (losses), net after tax	(116)	(132)
Expected Amortization, Prior service credits	(2)
Expected Amortization, Actuarial gain (losses), net	9
U. S. Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service credits before tax	2	3
Actuarial gain (losses), net before tax	7	8
Prior service credits after tax	1	2
Actuarial gain (losses), net after tax	4	$ 5
Expected Amortization, Prior service credits	(1)
Expected Amortization, Actuarial gain (losses), net	$ (1)