Summary of Change in Stockholder's Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Stockholders Equity Note [Line Items]
Balance at Beginning of Period	$ 1,203,450
Net Earnings	54,882	$ 45,344
Balance at End of Period	1,255,087
Common Stock [Member]
Stockholders Equity Note [Line Items]
Balance at Beginning of Period	485
Issuance of Restricted Stock	1
Stock Option Exercises	(1)
Balance at End of Period	485
Capital in Excess of Par Value [Member]
Stockholders Equity Note [Line Items]
Balance at Beginning of Period	149,014
Stock Compensation Expense	3,399
Cumulative Impact of the Adoption of ASU 2016-09	713
Shares Redeemed to Settle Employee Taxes	(1,378)
Stock Option Exercises	1,273
Purchase and Retirement of Common Stock	(1,880)
Balance at End of Period	151,141
Retained Earnings [Member]
Stockholders Equity Note [Line Items]
Balance at Beginning of Period	1,061,347
Dividends Declared to Stockholders	(4,856)
Cumulative Impact of the Adoption of ASU 2016-09	(713)
Net Earnings	54,882
Balance at End of Period	1,110,660
Accumulated Other Comprehensive Loss [Member]
Stockholders Equity Note [Line Items]
Balance at Beginning of Period	(7,396)
Change in Funded Status of Pension Plan, net of tax	197
Balance at End of Period	$ (7,199)