Pensions and Other Postemployment Benefits (OPEB) - Additional Information (Details) (Other Postemployment Benefits, USD $)
3 Months Ended 9 Months Ended
Jun. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Other Postemployment Benefits
     
Defined Benefit Plan Disclosure [Line Items]      
Recognized reduction in operating expenses due to curtailment $ 100,000 $ 0 $ 116,000
Reduction in liability due to curtailment $ 4,400,000