Employee Benefit Plans (Rollforward of Pension Plan Level 3 Assets) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	$ 4,357,000,000
Fair value of plan assets, end balance	4,316,000,000	$ 4,357,000,000
Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	648,000,000
Fair value of plan assets, end balance	575,000,000	648,000,000
Limited Partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	2,000,000
Fair value of plan assets, end balance		2,000,000
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	55,000,000
Fair value of plan assets, end balance	13,000,000	55,000,000
Preferred Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	6,000,000
Fair value of plan assets, end balance	7,000,000	6,000,000
Interest In Collective Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	1,589,000,000
Fair value of plan assets, end balance	1,888,000,000	1,589,000,000
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	10,000,000
Fair value of plan assets, end balance	7,000,000	10,000,000
Level 3 [Member] | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets, beginning balance	10,000,000	13,000,000
Net realized gain/(loss) on sale of investments	1,000,000	3,000,000
Purchases	4,000,000
Sales	(8,000,000)	(6,000,000)
Fair value of plan assets, end balance	$ 7,000,000	$ 10,000,000