Components of Income Tax Provision (Detail) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Mar. 31, 2019	[1]	Dec. 31, 2018	[1]	Sep. 30, 2018	[1]	Jun. 30, 2018	[1]	Mar. 31, 2018	[1],[2]	Dec. 31, 2017	[1],[2]	Sep. 30, 2017	[1],[2]	Jun. 30, 2017	[1],[2]	Mar. 31, 2019		Mar. 31, 2018		Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income (loss) before income taxes																	$ 223,340		$ 134,006		$ 78,172
Income (loss) before income taxes, foreign																	40,020		26,431		13,170
Income (loss) before income taxes																	263,360		160,437		91,342
Current income tax provision, Federal																			752		7,313
Current income tax provision, State																	564		1,491		5,045
Current income tax provision, Foreign																	11,525		3,400		1,066
Current income tax provision																	12,089		5,643		13,424
Deferred income tax provision, Federal																	(7,153)		38,848		23,008
Deferred income tax provision, State																	(1,503)		(1,014)		(349)
Deferred income tax provision, Foreign																	911		4,790		3,144
Deferred income tax provision																	(7,745)		42,624		25,803
Total income tax provision	$ 24,569		$ 19,648		$ 1,706		$ (41,579)		$ 11,660		$ 32,208		$ 7,981		$ (3,582)		$ 4,344	[1]	$ 48,267	[1],[2]	$ 39,227

[1] On December 22, 2017, the Tax Cuts and Jobs Act, or Tax Reform Act, was enacted into law. This new law, among other items, reduces the U.S. federal statutory corporate income tax rate from 35% to 21% effective January 1, 2018. During the year ended March 31, 2018, the Company recorded tax expense adjustments for $21.4 million related to the revaluation of its deferred taxes due to a reduction of the U.S. federal statutory corporate income tax rate.

[2] In the first quarter of fiscal 2018, the Company adopted ASU 2016-09, which requires that all excess tax benefits and tax deficiencies related share-based compensation arrangements be recognized as income tax benefit or expense, instead of in stockholders’ equity as previous guidance required. The income tax provision for the years ended March 31, 2019 and 2018 included excess tax benefits of $69.3 million and $31.0 million, respectively. These recognized excess tax benefits resulted from restricted stock units that vested or stock options that were exercised during the years ended March 31, 2019 and 2018.