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 (in shares) at Mar. 31, 2018		117,744,913			37,474,890
Beginning balance at Mar. 31, 2018	$ 2,068,782	$ 117	$ 2,665,120	$ 2,895	$ (995,843)	$ 396,493
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(88,932)					(88,932)
Unrealized net investment gains	23			23
Unrealized net gains (losses) on derivative financial instruments	(214)			(214)
Cumulative translation adjustments	(2,149)			(2,149)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,183,380
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	27,217		27,217
Issuance of common stock under employee stock purchase plan (in shares)		302,994
Issuance of common stock under employee stock purchase plan	7,575		7,575
Repurchase of treasury stock (in shares)					4,051,673
Repurchase of treasury stock	(9,855)		96,783		$ (106,638)
Ending balance (in shares) at Sep. 30, 2018		119,231,287			41,526,563
Ending balance at Sep. 30, 2018	2,036,598	$ 119	2,796,695	555	$ (1,102,481)	341,710
Beginning balance (in shares) at Jun. 30, 2018		118,139,282			37,604,005
Beginning balance at Jun. 30, 2018	2,045,201	$ 117	2,676,382	(107)	$ (999,329)	368,138
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(26,428)					(26,428)
Unrealized net investment gains	(5)			(5)
Unrealized net gains (losses) on derivative financial instruments	108			108
Cumulative translation adjustments	559			559
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		789,011
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	15,955		15,955
Issuance of common stock under employee stock purchase plan (in shares)		302,994
Issuance of common stock under employee stock purchase plan	7,575		7,575
Repurchase of treasury stock (in shares)					3,922,558
Repurchase of treasury stock	(6,369)		96,783		$ (103,152)
Issuance of shares, net
Ending balance (in shares) at Sep. 30, 2018		119,231,287			41,526,563
Ending balance at Sep. 30, 2018	2,036,598	$ 119	2,796,695	555	$ (1,102,481)	341,710
Beginning balance (in shares) at Mar. 31, 2019		119,760,132			42,149,771
Beginning balance at Mar. 31, 2019	2,065,433	$ 120	2,828,922	(2,639)	$ (1,119,063)	358,093
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(46,815)					(46,815)
Unrealized net investment gains	37			37
Unrealized net gains (losses) on derivative financial instruments	(11)			(11)
Cumulative translation adjustments	(1,086)			(1,086)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,590,980
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	27,488		27,488
Issuance of common stock under employee stock purchase plan (in shares)		297,635
Issuance of common stock under employee stock purchase plan	6,593		6,593
Repurchase of treasury stock (in shares)					4,660,929
Repurchase of treasury stock	(111,377)				$ (111,377)
Ending balance (in shares) at Sep. 30, 2019		121,648,747			46,810,700
Ending balance at Sep. 30, 2019	1,940,264	$ 122	2,863,003	(3,699)	$ (1,230,440)	311,278
Beginning balance (in shares) at Jun. 30, 2019		120,123,018			43,568,720
Beginning balance at Jun. 30, 2019	2,011,435	$ 120	2,841,001	(3,184)	$ (1,155,252)	328,750
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(17,472)					(17,472)
Unrealized net investment gains	2			2
Unrealized net gains (losses) on derivative financial instruments	8			8
Cumulative translation adjustments	(525)			(525)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,228,094
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	15,409		15,409
Issuance of common stock under employee stock purchase plan (in shares)		297,635
Issuance of common stock under employee stock purchase plan	6,593		6,593
Repurchase of treasury stock (in shares)					3,241,980
Repurchase of treasury stock	(75,188)				$ (75,188)
Ending balance (in shares) at Sep. 30, 2019		121,648,747			46,810,700
Ending balance at Sep. 30, 2019	$ 1,940,264	$ 122	$ 2,863,003	$ (3,699)	$ (1,230,440)	$ 311,278