Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock Voting	Additional Paid In Capital	Accumulated Other Comprehensive Income (Loss)	Treasury stock	Retained Earnings
Beginning Balance at Mar. 31, 2016	$ 2,443,382	$ 114	$ 2,642,745	$ (1,501)	$ (481,366)	$ 283,390
Beginning Balance (in shares) at Mar. 31, 2016		114,495,614			20,407,145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	33,291					33,291
Unrealized net investment gains	(59)			(59)
Unrealized net losses on derivative financial instruments	(54)			(54)
Cumulative translation adjustments	(1,000)			(1,000)
Recognition of actuarial net losses from pension and other post-retirement plan	(858)			(858)
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		950,159
Stock-based compensation expense for restricted stock units granted to employees	36,449		36,449
Issuance of common stock under employee stock purchase plan	15,697		15,697
Issuance of common stock under employee stock purchase plan (in shares)		471,658
Repurchase of treasury stock	(89,555)				$ (89,555)
Repurchase of treasury stock (in shares)					3,468,998
Shortfall from tax benefit from share-based compensation awards	(1,045)		(1,045)
Ending Balance at Mar. 31, 2017	2,436,250	$ 116	2,693,846	(3,472)	$ (570,921)	316,681
Ending Balance (in shares) at Mar. 31, 2017		115,917,431			23,876,143
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	79,812					79,812
Unrealized net investment gains	(6)			(6)
Unrealized net losses on derivative financial instruments	131			131
Cumulative translation adjustments	4,889			4,889
Recognition of actuarial net losses from pension and other post-retirement plan	1,353			1,353
Issuance of common stock pursuant to vesting of restricted stock units	1	$ 1
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,216,535
Stock-based compensation expense for restricted stock units granted to employees	43,425		43,425
Issuance of common stock under employee stock purchase plan	17,849		17,849
Issuance of common stock under employee stock purchase plan (in shares)		610,947
Repurchase of treasury stock	(514,922)		(90,000)		$ (424,922)
Repurchase of treasury stock (in shares)					13,598,747
Ending Balance at Mar. 31, 2018	2,068,782	$ 117	2,665,120	2,895	$ (995,843)	396,493
Ending Balance (in shares) at Mar. 31, 2018		117,744,913			37,474,890
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(73,324)					(73,324)
Unrealized net investment gains	60			60
Unrealized net losses on derivative financial instruments	(87)			(87)
Cumulative translation adjustments	(3,229)			(3,229)
Recognition of actuarial net losses from pension and other post-retirement plan	(2,278)			(2,278)
Issuance of common stock pursuant to vesting of restricted stock units	3	$ 3
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,438,219
Stock-based compensation expense for restricted stock units granted to employees	51,945		51,945
Issuance of common stock under employee stock purchase plan	15,074		15,074
Issuance of common stock under employee stock purchase plan (in shares)		577,000
Repurchase of treasury stock	(26,437)		96,783		$ (123,220)
Repurchase of treasury stock (in shares)					4,674,881
Ending Balance at Mar. 31, 2019	$ 2,065,433	$ 120	$ 2,828,922	$ (2,639)	$ (1,119,063)	$ 358,093
Ending Balance (in shares) at Mar. 31, 2019		119,760,132			42,149,771