Employee Benefit Plans (Summary of the Fair Value Measurements by Type of Asset) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Total	$ 81,427	$ 73,168	$ 71,174
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	374	340
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	81,053	72,828
Cash [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	374	340
Cash [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	374	340
Cash [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Large Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		13,306
U.S. Large Cap Growth [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Large Cap Growth [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		13,306
U.S. Small/Mid Cap Growth [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,111	5,655
U.S. Small/Mid Cap Growth [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Small/Mid Cap Growth [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,111	5,655
Non-U.S. Core [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	21,065	10,558
Non-U.S. Core [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
Non-U.S. Core [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	21,065	10,558
U.S. Large Cap Passive [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,717	7,364
U.S. Large Cap Passive [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Large Cap Passive [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,717	7,364
Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,052	652
Emerging Markets [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
Emerging Markets [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,052	652
U.S. Core Opportunistic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,284	24,438
U.S. Core Opportunistic [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Core Opportunistic [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	11,284	24,438
U.S. Passive [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	24,345	9,571
U.S. Passive [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
U.S. Passive [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	24,345	9,571
Opportunistic [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,479	1,254
Opportunistic [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total
Opportunistic [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 4,479	$ 1,254