Pension and Other Postretirement Benefits (Details 4) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Fair values of the pension plan assets by asset category
Total	$ 160,806
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	32
Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	160,774
Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Large cap equity funds [Member]
Fair values of the pension plan assets by asset category
Total	59,693
Large cap equity funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	0
Large cap equity funds [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	59,693
Large cap equity funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Mid cap equity funds [Member]
Fair values of the pension plan assets by asset category
Total	10,105
Mid cap equity funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	0
Mid cap equity funds [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	10,105
Mid cap equity funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Small cap equity funds [Member]
Fair values of the pension plan assets by asset category
Total	14,423
Small cap equity funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	0
Small cap equity funds [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	14,423
Small cap equity funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Government bond fund [Member]
Fair values of the pension plan assets by asset category
Total	23,270
Government bond fund [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	0
Government bond fund [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	23,270
Government bond fund [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Corporate bond fund [Member]
Fair values of the pension plan assets by asset category
Total	19,004
Corporate bond fund [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	0
Corporate bond fund [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	19,004
Corporate bond fund [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Fixed Income Funds [Member]
Fair values of the pension plan assets by asset category
Total	34,279
Fixed Income Funds [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	0
Fixed Income Funds [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	34,279
Fixed Income Funds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	0
Cash and Cash Equivalents [Member]
Fair values of the pension plan assets by asset category
Total	32
Cash and Cash Equivalents [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair values of the pension plan assets by asset category
Total	32
Cash and Cash Equivalents [Member] | Significant Observable Inputs (Level 2) [Member]
Fair values of the pension plan assets by asset category
Total	0
Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair values of the pension plan assets by asset category
Total	$ 0