Benefit Plans, Fair Value Disclosures (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 219	$ 206
Federal money market funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1	2
Mutual Funds - Fixed Income Securities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	77	55
Mutual Funds - Large Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	66	69
Mutual Funds - Mid Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	10	10
Mutual Funds - Blended Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6	6
Mutual Funds - Emerging Markets Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6	7
Common Collective Trust Funds - Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	17	16
Common Collective Trust Funds - Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	12	12
Common Collective Trust Funds - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	24	29
Quoted Prices in Active Markets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	166	149
Quoted Prices in Active Markets (Level 1) [Member] | Federal money market funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	1	2
Quoted Prices in Active Markets (Level 1) [Member] | Mutual Funds - Fixed Income Securities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	77	55
Quoted Prices in Active Markets (Level 1) [Member] | Mutual Funds - Large Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	66	69
Quoted Prices in Active Markets (Level 1) [Member] | Mutual Funds - Mid Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	10	10
Quoted Prices in Active Markets (Level 1) [Member] | Mutual Funds - Blended Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6	6
Quoted Prices in Active Markets (Level 1) [Member] | Mutual Funds - Emerging Markets Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	6	7
Quoted Prices in Active Markets (Level 1) [Member] | Common Collective Trust Funds - Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Quoted Prices in Active Markets (Level 1) [Member] | Common Collective Trust Funds - Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Quoted Prices in Active Markets (Level 1) [Member] | Common Collective Trust Funds - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	53	57
Significant Other Observable Inputs (Level 2) [Member] | Federal money market funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds - Fixed Income Securities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds - Large Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds - Mid Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds - Blended Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Mutual Funds - Emerging Markets Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Other Observable Inputs (Level 2) [Member] | Common Collective Trust Funds - Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	17	16
Significant Other Observable Inputs (Level 2) [Member] | Common Collective Trust Funds - Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	12	12
Significant Other Observable Inputs (Level 2) [Member] | Common Collective Trust Funds - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	24	29
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Federal money market funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds - Fixed Income Securities Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds - Large Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds - Mid Cap Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds - Blended Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Mutual Funds - Emerging Markets Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Collective Trust Funds - Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Collective Trust Funds - Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	0
Significant Unobservable Inputs (Level 3) [Member] | Common Collective Trust Funds - International [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0	$ 0