Retirement Plans - Target allocation ranges (Details)	12 Months Ended
	Dec. 31, 2016
United States Pension Plan Assets Defined Benefit | Domestic Equity Securities
Target allocation ranges
Target plan asset allocations range minimum	20.00%
Target plan asset allocations range maximum	35.00%
United States Pension Plan Assets Defined Benefit | International Equity Securities
Target allocation ranges
Target plan asset allocations range minimum	8.00%
Target plan asset allocations range maximum	19.00%
United States Pension Plan Assets Defined Benefit | Global equities
Target allocation ranges
Target plan asset allocations range minimum	0.00%
Target plan asset allocations range maximum	12.00%
United States Pension Plan Assets Defined Benefit | Debt securities
Target allocation ranges
Target plan asset allocations range minimum	27.00%
Target plan asset allocations range maximum	38.00%
United States Pension Plan Assets Defined Benefit | Real estate
Target allocation ranges
Target plan asset allocations range minimum	7.00%
Target plan asset allocations range maximum	13.00%
United States Pension Plan Assets Defined Benefit | Private investment partnerships
Target allocation ranges
Target plan asset allocations range minimum	5.00%
Target plan asset allocations range maximum	11.00%
United States Pension Plan Assets Defined Benefit | Hedge funds
Target allocation ranges
Target plan asset allocations range minimum	0.00%
Target plan asset allocations range maximum	5.00%
Non-U.S. Pension Plans Defined Benefit | Equity securities
Target allocation ranges
Target plan asset allocations range minimum	51.00%
Target plan asset allocations range maximum	74.00%
Non-U.S. Pension Plans Defined Benefit | Debt securities
Target allocation ranges
Target plan asset allocations range minimum	26.00%
Target plan asset allocations range maximum	46.00%
Non-U.S. Pension Plans Defined Benefit | Real estate
Target allocation ranges
Target plan asset allocations range minimum	3.00%
Target plan asset allocations range maximum	15.00%