Components of Income Tax Provision (Detail) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Mar. 31, 2018	[1],[2]	Dec. 31, 2017	[1],[2]	Sep. 30, 2017	[1],[2]	Jun. 30, 2017	[1],[2]	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018		Mar. 31, 2017	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income (loss) before income taxes													$ 134,006		$ 78,172	$ 54,406
Income (loss) before income taxes, foreign													26,431		13,170	11,432
Income (loss) before income taxes													160,437		91,342	65,838
Current income tax provision, Federal													752		7,313	1,690
Current income tax provision, State													1,491		5,045	2,113
Current income tax provision, Foreign													3,400		1,066	1,592
Current income tax provision													5,643		13,424	5,395
Deferred income tax provision, Federal													38,848		23,008	18,769
Deferred income tax provision, State													(1,014)		(349)	1,284
Deferred income tax provision, Foreign													4,790		3,144	2,243
Deferred income tax provision													42,624		25,803	22,296
Total income tax provision	$ 11,660		$ 32,208		$ 7,981		$ (3,582)		$ 14,457	$ 10,394	$ 5,861	$ 8,515	$ 48,267	[1],[2]	$ 39,227	$ 27,691

[1] In the first quarter of fiscal 2018, the Company adopted Accounting Standards Update No. 2016-09, Improvements to Employee Share-Based Payment Accounting, 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 benefit for the year ended March 31, 2018 included excess tax benefits of $31.0 million. These recognized excess tax benefits resulted from restricted stock units that vested or stock options that were exercised during the year ended March 31, 2018.

[2] 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.