Employee Benefit Plans (Pension Plan's Weighted-average Asset Allocations) (Details)	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan, Information about Plan Assets [Abstract]
Weighted average asset allocations	100.00%	100.00%
U.S. Equity [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Weighted average asset allocations	12.50%	27.00%
International Equity [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Weighted average asset allocations	15.10%	18.50%
Fixed Income [Member]
Defined Benefit Plan, Information about Plan Assets [Abstract]
Weighted average asset allocations	71.10%	52.50%
Money Market
Defined Benefit Plan, Information about Plan Assets [Abstract]
Weighted average asset allocations	1.30%	2.00%