Employee Benefit Plans Level 4 Benefit Payments (Details) $ in Millions	Dec. 31, 2015 USD ($)
Prescription Drug Subsidy Receipts, Rolling Maturity [Abstract]
Prescription Drug Subsidy Receipts, Next Twelve Months	$ 3
Prescription Drug Subsidy Receipts, Year Two	3
Prescription Drug Subsidy Receipts, Year Three	3
Prescription Drug Subsidy Receipts, Year Four	3
Prescription Drug Subsidy Receipts, Year Five	3
Prescription Drug Subsidy Receipts, after Year Five	18
Prescription Drug Subsidy Receipts Net	(33)
Pension Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Rolling Maturity [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	327
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	332
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	338
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	345
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	346
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	1,738
Net Defined Benefit Plan Expected Future Benefit Payments	(3,426)
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Expected Future Benefit Payments, Rolling Maturity [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	40
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	38
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	35
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	32
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	29
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	113
Net Defined Benefit Plan Expected Future Benefit Payments	$ (287)