CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Cash flows from operating activities:
Net income (loss)	$ (2,452)	$ 9,604
Adjustments to reconcile net income (loss) to net cash provided by (used for) operating activities:
Depreciation and amortization	2,605	2,613
Provisions for contracts, inventory and accounts receivable reserves	(270)	1,543
Amortization of bond premium	540	855
Deferred income taxes		1,894
Stock compensation expense	1,770	641
Changes in assets and liabilities:
Accounts receivable	4,878	7,490
Unbilled costs and fees	(3,272)	5
Inventories	(11,534)	(4,332)
Prepaid expenses and other assets	(5,436)	1,640
Accounts payable	(6,762)	2,873
Accrued income taxes	(2,338)	(2,094)
Customer deposits	5,433	12,731
Deferred revenue	(1,847)	(3,077)
Accrued expenses and other liabilities	(7,274)	(3,756)
Net cash (used for) provided by operating activities	(25,959)	28,630
Cash flows from investing activities:
Purchases of short-term investments	(29,212)	(18,311)
Proceeds from sales and maturities of short-term investments	40,933	57,534
Purchases of property and equipment, net	(943)	(1,249)
Net cash provided by investing activities	10,778	37,974
Cash flows from financing activities:
Decrease (increase) in restricted cash and investments	726	(1,222)
Proceeds from exercise of stock options	888	1,497
Repurchase of shares of common stock		(12,306)
Repayment of leasehold financing liability	(754)	(742)
Payment of common stock dividend	(7,993)	(7,800)
Reduction of income taxes paid due to the tax benefit from employee stock option expense		20
Net cash used for financing activities	(7,133)	(20,553)
Net (decrease) increase in cash and cash equivalents	(22,314)	46,051
Cash and cash equivalents at beginning of period	62,143	40,418
Cash and cash equivalents at end of period	$ 39,829	$ 86,469