Employee Benefit Plans (Pension Plan Assets Fair Value Hierarchy) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4,316,000,000	$ 4,357,000,000
Money Market Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	154,000,000	121,000,000
US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	324,000,000	294,000,000
Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	575,000,000	648,000,000
Corporate Debt | Non-agency mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29,000,000	34,000,000
Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	660,000,000	1,041,000,000
Preferred Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,000,000	6,000,000
Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	213,000,000	220,000,000
Interest In Collective Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,888,000,000	1,589,000,000
Limited Partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,000,000
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,000,000	55,000,000
Investments measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	482,000,000	381,000,000
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	976,000,000	1,306,000,000
Level 1 | Money Market Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	154,000,000	121,000,000
Level 1 | US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	186,000,000	147,000,000
Level 1 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	630,000,000	1,040,000,000
Level 1 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,000,000	2,000,000
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,000,000	(4,000,000)
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,851,000,000	2,660,000,000
Level 2 | US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	138,000,000	147,000,000
Level 2 | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	568,000,000	638,000,000
Level 2 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30,000,000	1,000,000
Level 2 | Preferred Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,000,000	6,000,000
Level 2 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	208,000,000	218,000,000
Level 2 | Interest In Collective Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,888,000,000	1,589,000,000
Level 2 | Limited Partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,000,000
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,000,000	59,000,000
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,000,000	10,000,000
Level 3 | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 7,000,000	$ 10,000,000	$ 13,000,000