Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Beginning balance	$ 128,053	$ 49,919	$ 48,019
Gross increases - tax positions in prior period	6,783	8,068	1,599
Gross decreases - tax positions in prior period	(21,409)	(5,700)	(2,185)
Gross increases - current-period tax positions	24,551	27,774	9,578
Increases from acquired businesses	39,420	60,796
Changes related to foreign currency translation adjustment and remeasurement	1,545	(1,087)
Decreases relating to settlements with taxing authorities and other	(686)	(3,933)	(6,689)
Decreases due to lapse of statute of limitations	(4,032)	(7,784)	(403)
Ending balance	$ 174,225	$ 128,053	$ 49,919