Pension Benefits and Other Postretirement Benefit Plans (Components of Net Periodic Benefit Cost) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Pension Benefits [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Interest cost $ 1,839 $ 2,018
Expected return on plan assets (2,771) (3,227)
Amortization of net loss 413 183
Settlement charge   110
Net periodic benefit cost (income) (519) (916)
Retirement Health and Life Insurance Benefits [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service cost 150 160
Interest cost 75 83
Amortization of prior service cost   0
Amortization of net loss   31
Net periodic benefit cost (income) $ 225 $ 274