CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Comprehensive income:
Net income	$ 239,277	$ 241,312
Pension and retiree medical benefits:
Amortization of losses included in net periodic benefit cost, net of tax of $615 and $142, respectively	948	211
Derivative instruments:
Net fair value decrease, net of tax of $0 and $(2), respectively	0	(4)
Reclassification of losses to net income, net of tax of $534 and $604, respectively	825	938
Total derivative instruments, net of tax	825	934
Other comprehensive income	1,773	1,145
Comprehensive income	$ 241,050	$ 242,457