Retirement Plans - Amortized amount from accumulated other comprehensive loss (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Pension Benefits
Amortized amount from accumulated other comprehensive loss
Net actuarial loss (gain)	$ 137
Prior service cost (credit)	15
Net periodic benefit cost	152
Postretirement Benefits Other Than Pensions
Amortized amount from accumulated other comprehensive loss
Net actuarial loss (gain)	(1)
Prior service cost (credit)	(8)
Net periodic benefit cost	$ (9)

Amount included in accumulated other comprehensive income (AOCI) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position, including gain (loss), prior service cost (credit), and transition asset (obligation).

No definition available.

Name:	us-gaap_DefinedBenefitPlanAmountToBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossNextFiscalYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration