Adoption of Accounting Standards Codification 606 - Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income	$ 673	$ 4,171	$ 1,591	$ 2,600	$ 9,484	$ 4,655	$ 3,823	$ 2,115	$ 9,035	$ 20,077	$ 25,261
Pension Adjustments:
Amortization of actuarial losses included in net income, net of tax benefit of $173, $302, and $283 for 2018, 2017, and 2016, respectively									570	508	479
Actuarial loss arising during the period, net of tax benefit of $302, for the year ended December 31, 2018									(899)	(304)	(650)
Interest rate cap hedges recognized in other comprehensive income, net of tax									407	(242)	(305)
Other Comprehensive (Loss) Income, Net of Tax									78	(38)	(476)
Comprehensive Income, Net of Tax									9,113	20,039	24,785
Amortization of actuarial (loss) gain, tax									(173)	(302)	(283)
Actuarial gain (loss) arising during the period, tax expense (benefit)									302	194	413
Unrealized gain (loss) on cash flow hedges, tax									121	$ (145)	$ (180)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income									(4,660)
Pension Adjustments:
Amortization of actuarial losses included in net income, net of tax benefit of $173, $302, and $283 for 2018, 2017, and 2016, respectively									0
Actuarial loss arising during the period, net of tax benefit of $302, for the year ended December 31, 2018									0
Interest rate cap hedges recognized in other comprehensive income, net of tax									0
Other Comprehensive (Loss) Income, Net of Tax									0
Comprehensive Income, Net of Tax									(4,660)
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net Income									4,375
Pension Adjustments:
Amortization of actuarial losses included in net income, net of tax benefit of $173, $302, and $283 for 2018, 2017, and 2016, respectively									570
Actuarial loss arising during the period, net of tax benefit of $302, for the year ended December 31, 2018									(899)
Interest rate cap hedges recognized in other comprehensive income, net of tax									407
Other Comprehensive (Loss) Income, Net of Tax									78
Comprehensive Income, Net of Tax									$ 4,453