Pensions and Other Post-retirement Benefits (Details 5) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	$ 163,436	$ 140,344
Cash [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	7,388	9,280
U.S. Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	54,691	46,004
International Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	22,683	19,096
Emerging Markets Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	14,786	10,784
Intermediate-term bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	26,749	22,684
Short-term bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	11,656	11,122
Global bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	12,854	10,999
Real estate fund [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	7,793	5,704
Multi-strategy hedge funds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	4,191	3,989
Private equity funds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	645	682
Level 1 [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	135,585	108,915
Level 1 [Member] | Cash [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	7,388	9,280
Level 1 [Member] | U.S. Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	45,025	37,859
Level 1 [Member] | International Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	19,650	9,355
Level 1 [Member] | Emerging Markets Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	14,535	10,569
Level 1 [Member] | Intermediate-term bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	18,378	14,673
Level 1 [Member] | Short-term bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	11,656	11,122
Level 1 [Member] | Global bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	11,185	10,353
Level 1 [Member] | Real estate fund [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	7,768	5,704
Level 2 [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	23,015	26,758
Level 2 [Member] | U.S. Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	9,666	8,145
Level 2 [Member] | International Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	3,033	9,741
Level 2 [Member] | Emerging Markets Equities [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	251	215
Level 2 [Member] | Intermediate-term bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	8,371	8,011
Level 2 [Member] | Global bonds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	1,669	646
Level 2 [Member] | Real estate fund [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	25
Level 3 [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	4,836	4,671
Level 3 [Member] | Multi-strategy hedge funds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	4,191	3,989
Level 3 [Member] | Private equity funds [Member]
Summary of fair values of the Company's defined benefit pension plan assets
Fair Value of Plan Assets	$ 645	$ 682