Pension and Other Postretirement Benefit Plans (Fair Value of Plan Assets by Category) (Details) (USD $) | Dec. 31, 2014 | Dec. 31, 2013 |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | $3,682,000,000 | $3,041,000,000 |
Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 535,000,000 | 335,000,000 |
Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 2,952,000,000 | 2,508,000,000 |
Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 195,000,000 | 198,000,000 |
Cash and Cash Equivalents | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 29,000,000 | 23,000,000 |
Cash and Cash Equivalents | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 29,000,000 | 23,000,000 |
Cash and Cash Equivalents | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Cash and Cash Equivalents | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
US Government Debt Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 579,000,000 | 432,000,000 |
US Government Debt Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
US Government Debt Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 579,000,000 | 432,000,000 |
US Government Debt Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Foreign Government Debt Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 253,000,000 | 131,000,000 |
Foreign Government Debt Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Foreign Government Debt Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 253,000,000 | 131,000,000 |
Foreign Government Debt Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Domestic Corporate Debt Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 1,000,000,000 | 850,000,000 |
Domestic Corporate Debt Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Domestic Corporate Debt Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 1,000,000,000 | 850,000,000 |
Domestic Corporate Debt Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Foreign Corporate Debt Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 321,000,000 | 193,000,000 |
Foreign Corporate Debt Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Foreign Corporate Debt Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 321,000,000 | 193,000,000 |
Foreign Corporate Debt Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
U.S. Equity Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 12,000,000 | 12,000,000 |
U.S. Equity Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 12,000,000 | 12,000,000 |
U.S. Equity Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
U.S. Equity Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Foreign Equity Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 427,000,000 | 223,000,000 |
Foreign Equity Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 427,000,000 | 223,000,000 |
Foreign Equity Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Foreign Equity Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Money Market Funds | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 67,000,000 | 77,000,000 |
Money Market Funds | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 67,000,000 | 77,000,000 |
Money Market Funds | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Money Market Funds | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Common and Collective Funds, U.S. equity securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 651,000,000 | 718,000,000 |
Common and Collective Funds, U.S. equity securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Common and Collective Funds, U.S. equity securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 651,000,000 | 718,000,000 |
Common and Collective Funds, U.S. equity securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Common and Collective Funds, International equity securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 66,000,000 | 79,000,000 |
Common and Collective Funds, International equity securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Common and Collective Funds, International equity securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 66,000,000 | 79,000,000 |
Common and Collective Funds, International equity securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Common and Collective Funds, Short-term investment fund | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 63,000,000 | 87,000,000 |
Common and Collective Funds, Short-term investment fund | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Common and Collective Funds, Short-term investment fund | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 63,000,000 | 87,000,000 |
Common and Collective Funds, Short-term investment fund | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnership, U.S. Equity Securities | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 140,000,000 | 145,000,000 |
Limited Partnership, U.S. Equity Securities | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnership, U.S. Equity Securities | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnership, U.S. Equity Securities | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 140,000,000 | 145,000,000 |
Limited Partnerships, Diversified fund of funds | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 32,000,000 | 35,000,000 |
Limited Partnerships, Diversified fund of funds | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnerships, Diversified fund of funds | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnerships, Diversified fund of funds | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 32,000,000 | 35,000,000 |
Limited Partnerships, Emerging growth | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 23,000,000 | 18,000,000 |
Limited Partnerships, Emerging growth | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnerships, Emerging growth | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Limited Partnerships, Emerging growth | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 23,000,000 | 18,000,000 |
Real Estate | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 10,000,000 | 11,000,000 |
Real Estate | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Real Estate | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 10,000,000 | 11,000,000 |
Real Estate | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Other Investments | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 9,000,000 | 7,000,000 |
Other Investments | Fair Value, Inputs, Level 1 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 0 | 0 |
Other Investments | Fair Value, Inputs, Level 2 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | 9,000,000 | 7,000,000 |
Other Investments | Fair Value, Inputs, Level 3 | | |
Defined Benefit Plan Disclosure [Line Items] | | |
Fair value of plan assets | $0 | $0 |