Employee Pension and Other Postretirement Benefits - Asset Allocation (Details)	12 Months Ended
	Dec. 31, 2015
Pension Benefits | Equity securities
Pension Plan and Other Postretirement Benefits Plan
Target plan asset allocation	63.00%
Pension Benefits | Debt Securities
Pension Plan and Other Postretirement Benefits Plan
Target plan asset allocation	25.00%
Pension Benefits | Real estate
Pension Plan and Other Postretirement Benefits Plan
Target plan asset allocation	12.00%
Other Benefits | Equity securities
Pension Plan and Other Postretirement Benefits Plan
Target plan asset allocation	70.00%
Other Benefits | Debt Securities
Pension Plan and Other Postretirement Benefits Plan
Target plan asset allocation	30.00%