Retirement Benefits - Fair Value Measurements of Pension and Postretirement Benefit Plan Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Derivative, notional amount	$ 1,491		$ 2,651
Net assets pending transactions excluded	42		43
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2,430		2,238		2,135
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	14,874		13,571		13,357
Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	226		115		108
Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,251		2,470		2,415
Equity Security Individually Held [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0		0
Equity Security Individually Held [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	2		2		0
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	0		0		0
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	272		41		0
Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		2		1
Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	904		806		754
Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	110		4		12
Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,329		1,039		1,235
Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	116		109		95
Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	744		582		426
Fair Value, Measurements, Recurring [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	17,261	[1],[2]	15,766	[1],[2]
Fair Value, Measurements, Recurring [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2,427	[2]	2,233	[2]
Fair Value, Measurements, Recurring [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	14,834	[2]	13,533	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	5,323	[1],[2]	5,368	[1],[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	767	[2]	831	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4,556	[2]	4,537	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	8,461	[1],[2]	7,813	[1],[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,434	[2]	1,287	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	7,027	[2]	6,526	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,477	[1],[2]	2,585	[1],[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	226	[2]	115	[2]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,251	[2]	2,470	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	11	[2]	51	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	11	[2]	51	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	674	[2]	641	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2,691	[2]	2,454	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	296	[2]	296	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,556	[2]	1,587	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	378	[2]	345	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,133	[2]	865	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Individually Held [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2	[2]	2	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	331	[2]	324	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2,021	[2]	2,075	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	184	[2]	154	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,705	[2]	1,773	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	147	[2]	170	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	316	[2]	302	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Equity Security Commingled Fund [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,005	[2]	965	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	4,712	[2]	4,529	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	480	[2]	450	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,261	[2]	3,360	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	525	[2]	515	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,449	[2]	1,167	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	2	[2]	2	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	74	[2]	63	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,139	[2]	1,007	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	15	[2]	17	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1,051	[2]	908	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	59	[2]	46	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	88	[2]	99	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	197	[2]	149	[2]
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	80	[2]	88	[2]
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	197	[2]	149	[2]
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	80	[2]	88	[2]
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
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Defined Benefit Plan, Fair Value of Plan Assets			2	[2]
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets			205	[2]
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0	[2]
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets			0	[2]
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Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			2	[2]
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			205	[2]
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0	[2]
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets			0	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	42	[2]	50	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
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Defined Benefit Plan, Fair Value of Plan Assets	3,245	[2]	2,968	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[2]	0	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	42	[2]	50	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	3,125	[2]	2,927	[2]
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
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Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
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[1] Excludes net assets of $42 million and $43 million at December 31, 2014 and 2013, respectively, which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities purchases.

[2] See Note 11—Fair Value of Financial Assets and Liabilities for a description of levels within the fair value hierarchy.

[3] Derivative instruments have a total notional amount of $1,491 million and $2,651 million at December 31, 2014 and 2013, respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of the company’s exposure to credit or market loss.