Stockholders' Equity and Noncontrolling Interests - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Dec. 07, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Class of Stock [Line Items]
Nonvested stock, weighted average remaining contractual term		26 months
Preferred stock, shares issued (in shares)		0	0
Preferred stock, shares outstanding (in shares)		0	0
Preferred stock, shares authorized (in shares)		1,000,000	1,000,000
Preferred stock, par value (usd per share)		$ 0.01	$ 0.01
Number of shares of common stock purchased		581,140	726,347	1,756,831
Repurchased common stock value		$ 34,561	$ 56,436	$ 121,191
Treasury stock, shares (in shares)		12,791,503	12,227,773
Shares issued in ESPP (USD per share)		$ 62.55	$ 62.55
Accelerated Share Repurchase Agreement [Member]
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares				1,495,714
Accelerated Share Repurchases, Settlement (Payment) or Receipt				$ 100,000
Accelerated Share Repurchases, Final Price Paid Per Share				$ 66.86
Alpha
Class of Stock [Line Items]
Initial purchase consideration	$ 750,000
Payments to acquire businesses	650,000
Shares issued in acquisition, value	$ 93,268
Shares issued in acquisition (USD per share)	$ 84.92
Common Stock | Alpha
Class of Stock [Line Items]
Shares issued in employee stock purchase plan (in shares)		17,410	3,256
Shares issued in acquisition (in shares)	1,177,630