Accumulated Other Comprehensive Income (Schedule of Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of revenue	$ 1,041,359	$ 971,700	$ 871,676
Tax expense (benefit)	94,426	80,695	117,788
Gains (losses), net of tax	427,792	377,047	263,269
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cost of revenue	10,628	(976)	27
Tax expense (benefit)	2,467	(187)	224
Gains (losses), net of tax	$ 8,161	$ (789)	$ (197)