Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Changes in Accumulated Other Comprehensive Loss
Balance, beginning of period	$ 440,092	$ 459,239
Balance, end of period	508,506	508,506
Accumulated Other Comprehensive Loss
Changes in Accumulated Other Comprehensive Loss
Balance, beginning of period	(8,056)	(5,076)
Other comprehensive income before reclassifications of gain (loss)	7,824	4,888
Amount of (loss) gain reclassified from accumulated other comprehensive income	(277)	(321)
Total other comprehensive (loss) income	7,547	4,567
Balance, end of period	(509)	(509)
Pension Plan
Changes in Accumulated Other Comprehensive Loss
Balance, beginning of period	(8,056)	(5,076)
Other comprehensive income before reclassifications of gain (loss)	2,403	(533)
Amount of (loss) gain reclassified from accumulated other comprehensive income	(43)	(87)
Total other comprehensive (loss) income	2,360	(620)
Balance, end of period	(5,696)	(5,696)
Derivatives Designated as Cash Flow Hedges
Changes in Accumulated Other Comprehensive Loss
Other comprehensive income before reclassifications of gain (loss)	5,421	5,421
Amount of (loss) gain reclassified from accumulated other comprehensive income	(234)	(234)
Total other comprehensive (loss) income	5,187	5,187
Balance, end of period	$ 5,187	$ 5,187