Computation of Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Basic Net Income Per Share
Net income	$ 61,868	$ 62,213	$ 44,588	$ 69,217	$ 13,071	$ 88,923	$ 168,669	$ 171,211
Weighted average shares – basic	45,201			45,140			45,105	45,225
Net income per share – basic	$ 1.37			$ 1.53			$ 3.74	$ 3.79
Diluted Net Income Per Share
Net income	$ 61,868	$ 62,213	$ 44,588	$ 69,217	$ 13,071	$ 88,923	$ 168,669	$ 171,211
Weighted average shares – basic	45,201			45,140			45,105	45,225
Effect of dilutive securities	505			555			548	710
Weighted average shares – diluted	45,706			45,695			45,653	45,935
Net income per share – diluted	$ 1.35			$ 1.51			$ 3.69	$ 3.73