CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Comprehensive income:
Net income	$ 195,164	$ 196,857	$ 456,385	$ 433,427
Pension and retiree medical benefits:
Amortization of losses included in net periodic benefit cost, net of tax of $550, $729, $1,099 and $3,232, respectively	864	1,135	1,728	496
Derivative instruments:
Net fair value increase (decrease), net of tax of $9, $(29), $6, and $(17), respectively	16	(44)	8	(31)
Reclassification of losses to net income, net of tax of $365, $451, $722 and $1,881, respectively	574	694	1,135	389
Total derivative instruments, net of tax	590	650	1,143	358
Marketable securities:
Net fair value increase (decrease), net of tax of $0, $0, $24 and $(18), respectively	0	0	38	(36)
Other comprehensive income	1,454	1,785	2,909	818
Comprehensive income	$ 196,618	$ 198,642	$ 459,294	$ 434,245