Comprehensive Income (Loss) Components of AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	$ (8,772)
Net current-period other comprehensive (loss) income	981	$ 942	$ (1,118)
Ending Balance	(9,934)	(8,772)
Reclassification of certain tax effects from AOCL				$ 2,100
Total
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	(8,772)	(9,714)
Other comprehensive income before reclassifications	270	(202)
Amounts reclassified from AOCL	213	773
Net current-period other comprehensive (loss) income	981	942
Ending Balance	(9,934)	(8,772)	(9,714)
Total | Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCL	498	371
Foreign Currency Translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	1,178	1,380
Other comprehensive income before reclassifications	270	(202)
Amounts reclassified from AOCL	0	0
Net current-period other comprehensive (loss) income	270	(202)
Ending Balance	1,448	1,178	1,380
Foreign Currency Translation | Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCL	0	0
Pension and Postretirement Medical Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	31	(742)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from AOCL	213	773
Net current-period other comprehensive (loss) income	213	773
Ending Balance	251	31	(742)
Pension and Postretirement Medical Plans | Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCL	0	0
Interest Rate Derivative Instruments Designated as Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning balance	(9,981)	(10,352)
Other comprehensive income before reclassifications	0	0
Amounts reclassified from AOCL	0	0
Net current-period other comprehensive (loss) income	498	371
Ending Balance	(11,633)	(9,981)	$ (10,352)
Interest Rate Derivative Instruments Designated as Cash Flow Hedges | Interest Expense [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCL	498	$ 371
Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of certain tax effects from AOCL	(2,143)
Foreign Currency Translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of certain tax effects from AOCL	0
Pension and Postretirement Medical Plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of certain tax effects from AOCL	7
Interest Rate Derivative Instruments Designated as Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of certain tax effects from AOCL	$ (2,150)