Employee Benefit Plans (Estimated Amortized Net Periodic Benefit For 2018) (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Other Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service cost	$ 14
Unrecognized net actuarial loss	(5)
Total	9
Pension Plans Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Unrecognized prior service cost	(6)
Unrecognized net actuarial loss	5
Total	$ (1)

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