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 income (loss)	(92,535)					(92,535)
Unrealized net investment gains	35			35
Unrealized net losses on derivative financial instruments	(219)			(219)
Cumulative translation adjustments	(3,319)			(3,319)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,369,122
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	40,423		40,423
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)					4,110,353
Repurchase of treasury stock	(11,416)		96,783		$ (108,199)
Ending balance (in shares) at Dec. 31, 2018		119,417,029			41,585,243
Ending balance at Dec. 31, 2018	2,043,477	$ 119	2,809,901	(608)	$ (1,104,042)	338,107
Beginning balance (in shares) at Sep. 30, 2018		119,231,287			41,526,563
Beginning balance at Sep. 30, 2018	2,036,598	$ 119	2,796,695	555	$ (1,102,481)	341,710
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(3,603)					(3,603)
Unrealized net investment gains	12			12
Unrealized net losses on derivative financial instruments	(5)			(5)
Cumulative translation adjustments	(1,170)			(1,170)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		185,742
Issuance of common stock pursuant to vesting of restricted stock units	0	$ 0
Stock-based compensation expense for restricted stock units granted to employees	13,206		13,206
Repurchase of treasury stock (in shares)					58,680
Repurchase of treasury stock	(1,561)				$ (1,561)
Ending balance (in shares) at Dec. 31, 2018		119,417,029			41,585,243
Ending balance at Dec. 31, 2018	2,043,477	$ 119	2,809,901	(608)	$ (1,104,042)	338,107
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 income (loss)	(10,090)					(10,090)
Unrealized net investment gains	40			40
Unrealized net losses on derivative financial instruments	43			43
Cumulative translation adjustments	(789)			(789)
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,621,350
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Stock-based compensation expense for restricted stock units granted to employees	38,187		38,187
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)					5,674,125
Repurchase of treasury stock	(136,612)				$ (136,612)
Ending balance (in shares) at Dec. 31, 2019		121,679,117			47,823,896
Ending balance at Dec. 31, 2019	1,962,807	$ 122	2,873,702	(3,345)	$ (1,255,675)	348,003
Beginning balance (in shares) at Sep. 30, 2019		121,648,747			46,810,700
Beginning balance at Sep. 30, 2019	1,940,264	$ 122	2,863,003	(3,699)	$ (1,230,440)	311,278
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	36,725					36,725
Unrealized net investment gains	3			3
Unrealized net losses on derivative financial instruments	54			54
Cumulative translation adjustments	297			297
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		30,370
Issuance of common stock pursuant to vesting of restricted stock units	0	$ 0
Stock-based compensation expense for restricted stock units granted to employees	10,699		10,699
Repurchase of treasury stock (in shares)					1,013,196
Repurchase of treasury stock	(25,235)				$ (25,235)
Ending balance (in shares) at Dec. 31, 2019		121,679,117			47,823,896
Ending balance at Dec. 31, 2019	$ 1,962,807	$ 122	$ 2,873,702	$ (3,345)	$ (1,255,675)	$ 348,003