Accumulated Other Comprehensive Income (Schedule of Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total cost of revenue	$ 971,700	$ 871,676	$ 799,987
Interest expense	34,744	37,225	32,049
Total (losses) gains before tax	457,742	381,057	321,846
Tax (benefits) expense	80,695	117,788	99,792
(Losses) gains, net of tax	377,047	263,269	222,054
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total cost of revenue	(976)	27	3,621
Interest expense	0	0	(421)
Total (losses) gains before tax	(976)	27	3,200
Tax (benefits) expense	(187)	224	949
(Losses) gains, net of tax	$ (789)	$ (197)	$ 2,251