CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Comprehensive income:
Net income	$ 261,221	$ 236,570
Pension and retiree medical benefits:
Amortization of losses (gains) included in net periodic benefit cost, net of tax of $550 and $2,503, respectively	864	(639)
Derivative instruments:
Net fair value (decrease) increase, net of tax of $(5) and $12, respectively	(7)	13
Reclassification of losses (gains) to net income, net of tax of $358 and $1,429, respectively	560	(305)
Total derivative instruments, net of tax	553	(292)
Marketable securities:
Net fair value increase (decrease), net of tax of $24 and $(18), respectively	38	(36)
Other comprehensive income (loss)	1,455	(967)
Comprehensive income	$ 262,676	$ 235,603