STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Net income	$ 24,470	$ 20,419	$ 118,130	$ 111,254
Other comprehensive income (loss), net of tax
Change in pension and postemployment benefit plan liability, net of tax of $(53) and (351), respectively	160	203	320	123
Other comprehensive income, net of tax	160	203	320	123
Comprehensive income	$ 24,630	$ 20,622	$ 118,450	$ 111,377