Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other comprehensive income/(loss), net of tax:
Unrealized loss on ash flow hedge, taxes	$ 809	$ 372
Net change in postretirement benefit plan, net of taxes	$ 127	$ 101	$ 434