Common Stock and Stock Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost charged against income	$ 79,599,000	$ 68,545,000	$ 55,775,000
Compensation costs capitalized	$ 11,900,000	$ 8,000,000.0	$ 6,600,000
Employee Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period over which unrecognized compensation cost is expected to be recognized	1 year 2 months 12 days
Award vesting period	4 years
Award contractual term	6 years
Weighted average estimated fair value of employee stock options granted	$ 18.35	$ 19.86	$ 23.62
Stock options exercised intrinsic value	$ 7,900,000	$ 5,200,000	$ 8,300,000
Tax benefit from stock options exercised			0
Total Shareholder Return Performance Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan description	During the third quarter of fiscal year 2018, the Company began granting TSR performance stock options to executive officers under the 1996 Equity Participation Plan. The number of shares of TSR performance stock options that will become eligible to vest based on the time-based vesting schedule described below is based on a comparison over a four-year performance period of the Company’s TSR to the TSR of the companies included in the S&P Mid Cap 400 Index. The number of options that may become vested and exercisable will range from 0% to 175% of the target number of options based on the Company’s relative TSR ranking for the performance period. The Company’s TSR performance stock options have a four-year time-based vesting schedule and a six year contractual term. The TSR performance stock options must be vested under both the time-based vesting schedule and the performance-based vesting conditions in order to become exercisable. Expense for TSR performance stock options that time-vest is recognized regardless of the actual TSR outcome achieved and is recognized on a graded-vesting basis.
Weighted average period over which unrecognized compensation cost is expected to be recognized	1 year 10 months 24 days
Award vesting period	4 years
Award contractual term	6 years
Weighted average estimated fair value of employee stock options granted	$ 32.32	$ 32.04
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost charged against income	$ 58,800,000	$ 54,000,000.0	$ 44,900,000
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years 7 months 6 days
Award vesting period	4 years
Weighted average estimated fair value of restricted stock units granted	$ 67.88	$ 72.89	$ 69.99
Total fair value of shares vested related to restricted stock units	$ 81,100,000	$ 64,600,000	$ 58,400,000
Equity Participation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares reserved for issuance				31,850,000
Plan description	Shares of the Company’s common stock granted under the Equity Participation Plan as an award other than as an option or as a stock appreciation right with a per share purchase price lower than 100% of fair market value on the date of grant are counted against the Equity Participation Plan share reserve as two shares for each share of common stock prior to September 22, 2010 and subsequent to September 19, 2012, and as 2.65 shares for each share of common stock during the period beginning on September 22, 2010 and ending on September 19, 2012.
Compensation cost charged against income	$ 75,300,000	65,100,000	52,600,000
Unrecognized compensation cost related to unvested stock-based compensation arrangements	$ 186,600,000
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares reserved for issuance	3,650,000
Discount on the fair market value of common stock purchased under the Employee Stock Purchase Plan	85.00%
Compensation cost charged against income	$ 4,300,000	$ 3,400,000	$ 3,100,000
Unrecognized compensation cost related to unvested stock-based compensation arrangements	$ 1,300,000
Weighted average period over which unrecognized compensation cost is expected to be recognized	6 months
Weighted average estimated fair value of employee stock purchase plan shares issued	$ 15.14	$ 15.09	$ 16.27