Benefit Plans (Schedule of Amounts Expected to be Amortized from AOCI into Net Periodic Pension Cost During Next Fiscal Year) (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Qualified Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ (66)
Net amount expected to be amortized in 2017	(66)
Nonqualified Plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	(12)
Net amount expected to be amortized in 2017	$ (12)

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