Financial Instruments - Schedule of Derivative Contracts on Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the consolidated statement of operations in which the effects of cash flow hedges are recorded in revenue	$ 1,511,983	$ 1,615,519	$ 2,169,461
Operating Expenses	792,887	891,988	958,349
Total amounts presented in the consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses	908,404	924,618	1,323,577
Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the consolidated statement of operations in which the effects of cash flow hedges are recorded in revenue	1,511,983	1,615,519	2,169,461
Operating Expenses	792,887
Total amounts presented in the consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses		891,988	958,349
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains on Cash Flow Hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Total amounts presented in the consolidated statement of operations in which the effects of cash flow hedges are recorded in operating expenses	0	(1,405)	17
Gain (loss) on foreign exchange contracts designated as cash flow hedges reclassified from OCI into revenue	$ 8,405	$ (18,532)	$ 10,153