Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total		Class A Common Stock	Treasury Stock		Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning balance (shares) at Mar. 31, 2018				158,028,673	(14,582,134)
Beginning of period at Mar. 31, 2018		$ 562,491		$ 1,580	$ (461,457)		$ 346,958	$ 690,516	$ (15,106)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)				489,385
Issuance of common stock		8,104		$ 6			8,098
Stock options exercised (shares)				755,294
Stock options exercised		9,371		$ 7			9,364
Repurchase of common stock (shares)				(3,600,000)	(3,719,344)	[1]
Repurchase of common stock		(172,267)	[1]	$ (168,400)	$ (172,267)	[1]
Net income		328,954						328,954
Other comprehensive income (loss), net of tax		(2,822)							(2,822)
Dividends paid per common share		(81,807)						(81,807)
Stock-based compensation expense		23,231					23,231
Ending balance (shares) at Dec. 31, 2018				159,273,352	(18,301,478)
End of period at Dec. 31, 2018		675,255		$ 1,593	$ (633,724)		387,651	937,663	(17,928)
Beginning balance (shares) at Sep. 30, 2018				159,124,212	(16,573,433)
Beginning of period at Sep. 30, 2018		646,340		$ 1,591	$ (550,688)		373,980	832,774	(11,317)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)				72,019
Issuance of common stock		2,877		$ 1			2,876
Stock options exercised (shares)				77,121
Stock options exercised		830		$ 1			829
Repurchase of common stock (shares)					(1,728,045)
Repurchase of common stock		(83,036)			$ (83,036)
Net income		132,037						132,037
Other comprehensive income (loss), net of tax		(6,611)							(6,611)
Dividends paid per common share		(27,148)						(27,148)
Stock-based compensation expense		9,966					9,966
Ending balance (shares) at Dec. 31, 2018				159,273,352	(18,301,478)
End of period at Dec. 31, 2018		675,255		$ 1,593	$ (633,724)		387,651	937,663	(17,928)
Beginning balance (shares) at Mar. 31, 2019				159,924,825	(19,896,972)
Beginning of period at Mar. 31, 2019		675,366		$ 1,599	$ (711,450)		401,596	994,811	(11,190)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)				305,782
Issuance of common stock		10,843		$ 3			10,840
Stock options exercised (shares)				428,174
Stock options exercised		7,440		$ 4			7,436
Repurchase of common stock (shares)				(400,000)	(443,763)	[2]
Repurchase of common stock		(30,885)	[2]	$ (28,400)	$ (30,885)	[2]
Recognition of liability related to future restricted stock units vesting		(350)					(350)
Net income		343,737						343,737
Other comprehensive income (loss), net of tax		(14,967)							(14,967)
Dividends paid per common share		(102,943)						(102,943)
Stock-based compensation expense		26,796					26,796
Ending balance (shares) at Dec. 31, 2019				160,658,781	(20,340,735)
End of period at Dec. 31, 2019		915,037		$ 1,606	$ (742,335)		446,318	1,235,605	(26,157)
Beginning balance (shares) at Sep. 30, 2019				160,400,357	(20,026,907)
Beginning of period at Sep. 30, 2019		840,183		$ 1,604	$ (719,793)		427,817	1,161,674	(31,119)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (shares)				59,549
Issuance of common stock		3,794		$ 0			3,794
Stock options exercised (shares)				198,875
Stock options exercised		3,753		$ 2			3,751
Repurchase of common stock (shares)	[1]				(313,828)
Repurchase of common stock	[1]	(22,542)			$ (22,542)
Recognition of liability related to future restricted stock units vesting		(32)					(32)
Net income		112,026						112,026
Other comprehensive income (loss), net of tax		4,962							4,962
Dividends paid per common share		(38,095)						(38,095)
Stock-based compensation expense		10,988					10,988
Ending balance (shares) at Dec. 31, 2019				160,658,781	(20,340,735)
End of period at Dec. 31, 2019		$ 915,037		$ 1,606	$ (742,335)		$ 446,318	$ 1,235,605	$ (26,157)

[1] During the nine months ended December 31, 2018, the Company purchased 3.6 million shares of the Company’s Class A Common Stock in a series of open market transactions for $168.4 million. Additionally, the Company repurchased shares during the first quarter of fiscal 2019 to cover the minimum statutory withholding taxes on restricted stock units that vested on June 30, 2018.

[2] During the nine months ended December 31, 2019, the Company purchased 0.4 million shares of the Company’s Class A Common Stock in a series of open market transactions for $28.4 million. Additionally, the Company repurchased shares during the first, second, and third quarters of fiscal 2020 to cover the minimum statutory withholding taxes on restricted stock units that vested on various dates during the period.