Pension, Postretirement and Postemployment Benefits (Details 2) (Pension Benefits, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	$ 23,534	$ 21,384	$ 18,780
Cash
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	745
Equity Securities
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	13,056
Debt Securities
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	9,733
Short-term Investments.
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	22,789
Fair Value, Inputs, Level 2
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	23,534
Fair Value, Inputs, Level 2 | Cash
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	745
Fair Value, Inputs, Level 2 | Equity Securities
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	13,056
Fair Value, Inputs, Level 2 | Debt Securities
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	9,733
Fair Value, Inputs, Level 2 | Short-term Investments.
Pension, Postretirement and Postemployment Benefits
Fair Value of Plan assets	$ 22,789