Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 210,910	$ 222,736
Other comprehensive income:
Net gain on cash flow hedges	5,414	1,295
Reclassification of net loss on cash flow hedges to income	740	740
Net actuarial loss	(5,944)	0
Amortization of prior service credit	(45)	(45)
Amortization of actuarial loss	5,114	1,228
Settlement cost	0	1,365
Total other comprehensive income	5,279	4,583
Comprehensive income	$ 216,189	$ 227,319