Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 253,703	$ 214,409	$ 461,366	$ 425,319
Other comprehensive income (loss):
Net gain (loss) on cash flow hedges	(6,659)	1,697	(11,035)	7,111
Reclassification of net loss on cash flow hedges to income	601	739	1,228	1,479
Net actuarial gain (loss)	(10,913)	653	(10,913)	(5,291)
Amortization of prior service credit	(45)	(46)	(90)	(91)
Amortization of actuarial loss	1,625	1,703	2,973	6,817
Settlement cost	2,060	0	2,060	0
Total other comprehensive income (loss)	(13,331)	4,746	(15,777)	10,025
Comprehensive income	$ 240,372	$ 219,155	$ 445,589	$ 435,344