Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 869,531		$ 802,771	$ 819,122
Other comprehensive income:
Net loss on cash flow hedges(1)	(1,937)	[1]	(6,699)	(14,904)
Reclassification of net loss (gain) on cash flow hedges to income(1)	2,958	[1]	2,049	1,365
Net actuarial loss(2)	(46,008)	[2]	(2,452)	(8,359)
Plan amendment(2)	0	[2]	0	3,610
Amortization of prior service credit(2)	(181)	[2]	(3,516)	(3,713)
Amortization of actuarial loss(2)	6,371	[2]	5,525	7,191
Settlement cost(2)	2,460	[2]	202	0
Total other comprehensive loss	(36,337)		(4,891)	(14,810)
Comprehensive income	$ 833,194		$ 797,880	$ 804,312

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