Employee Benefit Plans (Details 4) (Pension Benefits [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Fair values of pension plan assets
Total assets at fair value	$ 965	$ 971	$ 860
Cash management fund [Member]
Fair values of pension plan assets
Total assets at fair value	43	30
U.S. large cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	170	192
U.S. small cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	121	137
International developed markets large cap growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	61	72
Emerging markets growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	12	16
Equities - U.S. large cap [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	147	168
Equities - Emerging markets value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	27	35
Equities - International developed markets large cap value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	69	80
Fixed income - Corporate bonds [Member] | Commingled investment funds - fixed income [Member]
Fair values of pension plan assets
Total assets at fair value	58
U.S. Treasury securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	16	20
Mortgage-backed securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	65	64
Corporate bonds [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	169	150
Insurance company investment contracts and other [Member]
Fair values of pension plan assets
Total assets at fair value	7	7
Level 1 [Member]
Fair values of pension plan assets
Total assets at fair value	357	384
Level 1 [Member] | Cash management fund [Member]
Fair values of pension plan assets
Total assets at fair value	43	30
Level 1 [Member] | U.S. large cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	170	192
Level 1 [Member] | U.S. small cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	121	137
Level 1 [Member] | International developed markets large cap growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	4	4
Level 1 [Member] | Emerging markets growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	3	4
Level 1 [Member] | Equities - U.S. large cap [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 1 [Member] | Equities - Emerging markets value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 1 [Member] | Equities - International developed markets large cap value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 1 [Member] | Fixed income - Corporate bonds [Member] | Commingled investment funds - fixed income [Member]
Fair values of pension plan assets
Total assets at fair value	0
Level 1 [Member] | U.S. Treasury securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	16	17
Level 1 [Member] | Mortgage-backed securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 1 [Member] | Corporate bonds [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 1 [Member] | Insurance company investment contracts and other [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 2 [Member]
Fair values of pension plan assets
Total assets at fair value	608	587
Level 2 [Member] | Cash management fund [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 2 [Member] | U.S. large cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 2 [Member] | U.S. small cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 2 [Member] | International developed markets large cap growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	57	68
Level 2 [Member] | Emerging markets growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	9	12
Level 2 [Member] | Equities - U.S. large cap [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	147	168
Level 2 [Member] | Equities - Emerging markets value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	27	35
Level 2 [Member] | Equities - International developed markets large cap value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	69	80
Level 2 [Member] | Fixed income - Corporate bonds [Member] | Commingled investment funds - fixed income [Member]
Fair values of pension plan assets
Total assets at fair value	58
Level 2 [Member] | U.S. Treasury securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	3
Level 2 [Member] | Mortgage-backed securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	65	64
Level 2 [Member] | Corporate bonds [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	169	150
Level 2 [Member] | Insurance company investment contracts and other [Member]
Fair values of pension plan assets
Total assets at fair value	7	7
Level 3 [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Cash management fund [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | U.S. large cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | U.S. small cap [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | International developed markets large cap growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Emerging markets growth [Member] | Equity securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Equities - U.S. large cap [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Equities - Emerging markets value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Equities - International developed markets large cap value [Member] | Commingled investment funds - equities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Fixed income - Corporate bonds [Member] | Commingled investment funds - fixed income [Member]
Fair values of pension plan assets
Total assets at fair value	0
Level 3 [Member] | U.S. Treasury securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Mortgage-backed securities [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Corporate bonds [Member] | Fixed income securities [Member]
Fair values of pension plan assets
Total assets at fair value	0	0
Level 3 [Member] | Insurance company investment contracts and other [Member]
Fair values of pension plan assets
Total assets at fair value	$ 0	$ 0