Employee Benefit Plans (Estimated Amortization of Unamortized Actuarial Gains and Losses - 2016) (Details)	12 Months Ended
	Dec. 31, 2015 USD ($)
Qualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)	$ (7,000,000)
Net actuarial loss	45,000,000
Total estimated amortization of unamortized actuarial gains and losses	38,000,000
Nonqualified Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	4,000,000
Total estimated amortization of unamortized actuarial gains and losses	4,000,000
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)	(1,000,000)
Total estimated amortization of unamortized actuarial gains and losses	$ (1,000,000)