Retirement Plans (Asset Allocations) (Details)	Dec. 31, 2016	Dec. 31, 2015
Asset category [Abstract]
Weighted average asset allocation (in hundreths)	100.00%	100.00%
Equity Securities [Member]
Asset category [Abstract]
Weighted average asset allocation (in hundreths)	50.00%	47.00%
Debt Securities [Member]
Asset category [Abstract]
Weighted average asset allocation (in hundreths)	38.00%	46.00%
Alternative Investments [Member]
Asset category [Abstract]
Weighted average asset allocation (in hundreths)	11.00%	6.00%
Cash and Cash Equivalents [Member]
Asset category [Abstract]
Weighted average asset allocation (in hundreths)	1.00%	1.00%