Employee Benefits (Details 5) (Pension Benefits, USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined benefit pension plan disclosure
Fair value of plan assets	$ 82,163	$ 87,960	$ 81,234
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	82,163
Cash
Defined benefit pension plan disclosure
Fair value of plan assets	1,380	1,297
Cash | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	1,380
Equity Security - Mutual Funds: Large-Cap
Defined benefit pension plan disclosure
Fair value of plan assets	6,810	18,600
Equity Security - Mutual Funds: Large-Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	6,810
Equity Security - Mutual Funds: Mid-Cap
Defined benefit pension plan disclosure
Fair value of plan assets	2,846	3,152
Equity Security - Mutual Funds: Mid-Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	2,846
Equity Security - Mutual Funds: Small-Cap
Defined benefit pension plan disclosure
Fair value of plan assets	2,923	3,186
Equity Security - Mutual Funds: Small-Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	2,923
Equity Security - Mutual Funds: Mixed-Cap
Defined benefit pension plan disclosure
Fair value of plan assets	16,042	6,421
Equity Security - Mutual Funds: Mixed-Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	16,042
Equity Security - Mutual Funds: International
Defined benefit pension plan disclosure
Fair value of plan assets	9,630	12,003
Equity Security - Mutual Funds: International | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	9,630
Equity Security - Mutual Funds: Emerging Market
Defined benefit pension plan disclosure
Fair value of plan assets	5,123	5,467
Equity Security - Mutual Funds: Emerging Market | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	5,123
Fixed Income - Mutual Funds
Defined benefit pension plan disclosure
Fair value of plan assets	37,409	37,834
Fixed Income - Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	$ 37,409