Employee Benefit Plans (Schedule of Allocation of Plan Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017		Dec. 31, 2016
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 103,236		$ 84,770
Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 103,106	[1]	$ 84,671	[2]
U.S. Equity Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	27.00%		28.00%
U.S. Fixed Income Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	36.00%		37.00%
Non-U.S. Equity Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	22.00%		20.00%
Other [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations	15.00%		15.00%
Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 130		$ 99
Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	103,236		84,770
Fair Value, Inputs, Level 1 [Member] | Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	103,106	[1]	84,671	[2]
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	130		99
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Fair Value, Inputs, Level 2 [Member] | Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[1]	0	[2]
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0		0
Fair Value, Inputs, Level 3 [Member] | Mutual Funds [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	0	[1]	0	[2]
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Defined Benefit Plan Change In Benefit Obligation [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	$ 0		$ 0

[1] Mutual funds were invested 27% in U.S. equity funds, 36% in U.S. fixed income funds, 22% in non-U.S. equity funds and 15% in other.

[2] Mutual funds were invested 28% in U.S. equity funds, 37% in U.S. fixed income funds, 20% in non-U.S. equity funds and 15% in other.