Employee Benefit Plans (Pension Plan Assets Fair Value Hierarchy) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 4,357,000,000	$ 4,252,000,000
Money Market Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	121,000,000	130,000,000
US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	294,000,000	316,000,000
Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	648,000,000	751,000,000
Corporate Debt | Non-agency mortgage backed securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63,000,000	84,000,000
Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	220,000,000	199,000,000
Interest In Collective Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,698,000,000	1,572,000,000
Limited Partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	274,000,000	184,000,000
Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,041,000,000	1,055,000,000
Preferred Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,000,000	15,000,000
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55,000,000	30,000,000
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,306,000,000	1,379,000,000
Level 1 | Money Market Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	121,000,000	130,000,000
Level 1 | US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	147,000,000	192,000,000
Level 1 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,000,000	4,000,000
Level 1 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,040,000,000	1,053,000,000
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(4,000,000)
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,660,000,000	2,580,000,000
Level 2 | US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	147,000,000	124,000,000
Level 2 | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	638,000,000	738,000,000
Level 2 | Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	218,000,000	195,000,000
Level 2 | Interest In Collective Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,589,000,000	1,474,000,000
Level 2 | Limited Partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,000,000	2,000,000
Level 2 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,000,000	2,000,000
Level 2 | Preferred Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,000,000	15,000,000
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	59,000,000	30,000,000
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	391,000,000	293,000,000
Level 3 | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,000,000	13,000,000	22,000,000
Level 3 | Interest In Collective Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	109,000,000	98,000,000	88,000,000
Level 3 | Limited Partnerships
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 272,000,000	$ 182,000,000	$ 127,000,000