Retirement Plans - Weighted Average Asset Allocations (Details) - Pension Plans, Defined Benefit [Member]	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	100.00%	100.00%
U.S. Equities securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	72.00%	83.00%
U.S. Debt securities [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	24.00%	15.00%
Cash [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Weighted average asset allocations	4.00%	2.00%