Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings
Beginning Balance at Dec. 31, 2017	$ 3,581,956	$ 1,871,396	$ (20,557)	$ 1,731,117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options		82,414
Stock-based compensation expense		149,627
Other comprehensive income (loss)			8,130
Net income	674,473			674,473
Ending Balance at Jun. 30, 2018	4,496,600	2,103,437	(12,427)	2,405,590
Beginning Balance at Mar. 31, 2018	4,020,730	1,995,225	4,264	2,021,241
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options		26,980
Stock-based compensation expense		81,232
Other comprehensive income (loss)			(16,691)
Net income	384,349			384,349
Ending Balance at Jun. 30, 2018	4,496,600	2,103,437	(12,427)	2,405,590
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU 2016-02, Leases (Topic 842)				2,474
Beginning Balance at Dec. 31, 2018	5,238,765	2,315,988	(19,582)	2,942,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options		45,329
Stock-based compensation expense		205,048
Other comprehensive income (loss)			(770)
Net income	614,702
Ending Balance at Jun. 30, 2019	6,105,548	2,566,365	(20,352)	3,559,535
Beginning Balance at Mar. 31, 2019	5,703,058	2,439,773	(25,600)	3,288,885
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of options		22,744
Stock-based compensation expense		103,848
Other comprehensive income (loss)			5,248
Net income	270,650			270,650
Ending Balance at Jun. 30, 2019	$ 6,105,548	$ 2,566,365	$ (20,352)	$ 3,559,535