Summary of Significant Accounting Policies - Impact on Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (26,704)	$ (116,846)	[1],[2]	$ (414,249)	[1],[2]
Adjustments to reconcile net loss to net cash provided by operating activities:
Amortization of deferred commissions	143,358	99,105	[2]	69,565	[2]
Deferred income tax	(34,180)	(5,724)	[2]	(658)	[2]
Changes in operating assets and liabilities, net of effect of business combinations:
Accounts receivable	(146,148)	(99,693)	[2]	(126,415)	[2]
Deferred commissions	(239,382)	(190,246)	[2]	(151,921)	[2]
Prepaid expenses and other assets	(19,886)	(34,288)	[2]	(24,164)	[2]
Deferred revenue	468,856	369,242	[2]	285,139	[2]
Accrued expenses and other liabilities	82,071	66,526	[2]	87,560	[2]
Net cash provided by operating activities	811,089	642,940	[2]	159,081	[2]
Foreign currency effect on cash, cash equivalents and restricted cash	$ (15,530)	28,013	[2]	(5,945)	[2]
Previously Reported
Cash flows from operating activities:
Net loss		(149,130)		(451,804)
Adjustments to reconcile net loss to net cash provided by operating activities:
Amortization of deferred commissions		115,262		81,217
Deferred income tax		(9,078)		(3,424)
Changes in operating assets and liabilities, net of effect of business combinations:
Accounts receivable		(98,432)		(125,106)
Deferred commissions		(174,503)		(136,459)
Prepaid expenses and other assets		(46,138)		(21,500)
Deferred revenue		381,562		300,167
Accrued expenses and other liabilities		68,344		82,681
Net cash provided by operating activities		642,825		159,921
Foreign currency effect on cash, cash equivalents and restricted cash		$ 28,128		$ (6,785)

[1] As adjusted to reflect the impact of the full retrospective adoption of Topic 606.

[2] As adjusted to reflect the impact of the full retrospective adoption of Topic 606.