Basis of Preparation and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Apr. 01, 2017
Summary Of Significant Accounting Policy [Line Items]
Cumulative effect to increase retained earnings and deferred tax assets				$ 77,081
Excess tax benefits related to restricted stock unit vestings or stock option exercises, decrease in financing activities			$ 3,631
Excess tax benefits related to restricted stock unit vestings or stock option exercises, increase in operating activities			$ 3,631
ASU 2016-09
Summary Of Significant Accounting Policy [Line Items]
Excess tax benefit	$ 4,500	$ 21,300
Excess tax benefits related to restricted stock unit vestings or stock option exercises, decrease in financing activities		21,300
Excess tax benefits related to restricted stock unit vestings or stock option exercises, increase in operating activities		$ 21,300
Increase additional paid in capital				1,800
Increase deferred tax assets				700
Decrease retained earnings				(1,100)
Adjustment to Increase Retained Earnings and Deferred Tax Assets | ASU 2016-09
Summary Of Significant Accounting Policy [Line Items]
Cumulative effect to increase retained earnings and deferred tax assets				$ 76,400