Consolidated Statements Of Stockholders' Equity And Comprehensive Income (USD $) In Thousands, except Share data	Common Stock Voting [Member]	Additional Paid In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Comprehensive Income [Member]	Total
Balance at Mar. 31, 2009	$ 45	$ 192,844	$ (1,461)	$ (28,939)	$ 63,242		$ 225,731
Balance, shares at Mar. 31, 2009	44,811,729			4,532,017
Net income					27,917	27,917	27,917
Unrealized investment gains (losses), net of tax			(196)			(196)	(196)
Unrealized gains (losses) on derivative financial instruments, net of tax			(160)			(160)	(160)
Comprehensive income						27,561
Issuance of common stock pursuant to exercise of options, shares	1,026,771
Issuance of common stock pursuant to exercise of options	1	5,790					5,791
Issuance of common stock pursuant to vesting of restricted stock units and repurchase of common stock for net settlements, shares	651,666			188,567
Issuance of common stock pursuant to vesting of restricted stock units and repurchase of common stock for net settlements	0			(2,752)			(2,752)
Stock-based compensation expense for stock options granted to employees		10					10
Stock-based compensation expense for restricted stock units granted to employees		5,446					5,446
Tax benefits of disqualifying dispositions of incentive stock options		5,056					5,056
Balance at Mar. 31, 2010	46	209,146	(1,817)	(31,691)	91,159		266,843
Balance, shares at Mar. 31, 2010	46,490,166			4,720,584
Net income					37,265	37,265	37,265
Unrealized investment gains (losses), net of tax			936			936	936
Unrealized gains (losses) on derivative financial instruments, net of tax			205			205	205
Comprehensive income						38,406
Issuance of common stock pursuant to exercise of options, shares	450,432
Issuance of common stock pursuant to exercise of options	1	3,378					3,379
Issuance of common stock pursuant to vesting of restricted stock units and repurchase of common stock for net settlements, shares	501,281			164,074
Issuance of common stock pursuant to vesting of restricted stock units and repurchase of common stock for net settlements	0			(3,746)			(3,746)
Stock-based compensation expense for restricted stock units granted to employees		6,439					6,439
Tax benefits of disqualifying dispositions of incentive stock options		8,238					8,238
Balance at Mar. 31, 2011	47	227,201	(676)	(35,437)	128,424		319,559
Balance, shares at Mar. 31, 2011	47,441,879			4,884,658			47,441,879
Net income					32,428	32,428	32,428
Unrealized investment gains (losses), net of tax			1,357			1,357	1,357
Unrealized gains (losses) on derivative financial instruments, net of tax			(84)			(84)	(84)
Cumulative translation adjustments			(385)			(385)	(385)
Comprehensive income						33,316
Issuance of common stock pursuant to exercise of options, shares	84,502						84,502
Issuance of common stock pursuant to exercise of options	0	472					472
Issuance of common stock pursuant to vesting of restricted stock units and repurchase of common stock for net settlements, shares	659,350
Issuance of common stock pursuant to vesting of restricted stock units and repurchase of common stock for net settlements	1						1
Stock-based compensation expense for restricted stock units granted to employees		8,651					8,651
Repurchase of treasury stock, shares				1,486,882
Repurchase of treasury stock				(20,595)			(20,595)
Tax benefits of disqualifying dispositions of incentive stock options		965					965
Balance at Mar. 31, 2012	$ 48	$ 237,289	$ 212	$ (56,032)	$ 160,852		$ 342,369
Balance, shares at Mar. 31, 2012	48,185,731			6,371,540			48,185,731