CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 467,468	$ 451,779	$ 257,692
Other comprehensive income, net of tax:
Foreign currency translation adjustment, net of tax of $0, $0, $0	(10,991)	(28,442)	37,840
Available-for-sale marketable securities:
Unrealized gains (losses) on debt securities arising during period, net of tax of $1,659, $(722), $1,903, respectively	6,015	(2,110)	1,863
Less: Reclassification adjustment for (gains) losses included in net income, net of tax of $(192), $(21), $(297), respectively	(690)	1,337	(441)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Total	5,325	(773)	1,422
Defined benefit pension and post-retirement plans:
Amortization of prior service benefit included in net periodic pension and post-retirement benefit, net of tax $(43), $(71), $(154), respectively	(148)	(245)	(272)
Other comprehensive (loss) income	(5,814)	(29,460)	38,990
Comprehensive income	$ 461,654	$ 422,319	$ 296,682