Benefits 8 (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Asset category [Abstract]
Fair value of plan assets	$ 110,222	$ 102,146
Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets	2,476
Mutual fund [Member]
Asset category [Abstract]
Fair value of plan assets	107,746	99,843
Pension member
Asset category [Abstract]
Fair value of plan assets	132,795	127,000
Pension member | Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets	11,791	4,901
Pension member | Mutual fund [Member]
Asset category [Abstract]
Fair value of plan assets	110,632	111,829
Pension member | Multi-strategy hedge funds
Asset category [Abstract]
Fair value of plan assets	10,372	10,270
OPEB member | Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets		2,303
Level 1 [Member] | Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets		2,303
Level 1 [Member] | Pension member
Asset category [Abstract]
Fair value of plan assets	11,791	4,901
Level 1 [Member] | Pension member | Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets	11,791	4,901
Level 1 [Member] | Pension member | Mutual fund [Member]
Asset category [Abstract]
Fair value of plan assets	0	0
Level 1 [Member] | Pension member | Multi-strategy hedge funds
Asset category [Abstract]
Fair value of plan assets	0	0
Level 1 [Member] | OPEB member | Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets	2,476
Level 2 [Member] | Pension member
Asset category [Abstract]
Fair value of plan assets	121,004	122,099
Level 2 [Member] | Pension member | Cash and cash equivalents
Asset category [Abstract]
Fair value of plan assets	0	0
Level 2 [Member] | Pension member | Mutual fund [Member]
Asset category [Abstract]
Fair value of plan assets	110,632	111,829
Level 2 [Member] | Pension member | Multi-strategy hedge funds
Asset category [Abstract]
Fair value of plan assets	$ 10,372	$ 10,270