CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 81,001	$ 95,235	$ 73,380
Other comprehensive income (loss), net of tax:
Defined benefit pension plan—amortization of net income (loss), net of tax of $116, $(1) and $36, respectively	376	(78)	67
Other comprehensive income (loss)	376	(78)	67
Comprehensive income, net of tax	$ 81,377	$ 95,157	$ 73,447