STATEMENTS OF COMPREHENSIVE INCOME STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net income	$ 18,797	$ 12,737	$ 115,876	$ 97,781
Other comprehensive income (loss), net of tax
Change in pension and postemployment benefit plan liability, net of tax of $(81), $(72), $(242), and $(217), respectively respectively	128	116	386	347
Other comprehensive income, net of tax	128	116	386	347
Comprehensive income	$ 18,925	$ 12,853	$ 116,262	$ 98,128