CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 17,454	$ 21,422	$ 42,817
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,114	5,768	4,961
Provisions for contracts, inventory, and accounts receivable reserves	5,405	2,998	1,608
Amortization of bond premium	2,700	2,689	2,057
Stock compensation expense	184	1,799	5,216
Other	(59)	(47)	(125)
Deferred income taxes	(2,966)	1,750	(2,716)
Change in assets and liabilities:
Accounts receivable	(3,382)	11,819	551
Unbilled costs and fees	(1,669)	13,876	(15,004)
Inventories	(4,933)	(4,333)	(3,139)
Prepaid expenses and other assets	813	(3,609)	3,048
Accrued income taxes	2,094	(1,936)	(2,267)
Accounts payable	910	(1,917)	(1,592)
Deferred revenue	1,661	(568)	(2,034)
Customer deposits	1,168	5,838	(4,521)
Accrued expenses and other current liabilities	6,663	(4,530)	4,344
Total adjustments	13,703	29,597	(9,613)
Net cash provided by operating activities	31,157	51,019	33,204
Cash flows from investing activities:
Proceeds from sales and maturities of short-term investments	200,089	220,293	192,406
Purchases of short-term instruments	(140,532)	(283,685)	(160,422)
Proceeds from sale of fixed assets	110	51	3
Purchases of property and equipment	(3,618)	(5,211)	(5,304)
Net cash provided by (used for) investing activities	56,049	(68,552)	26,683
Cash flows from financing activities:
Decrease (increase) in restricted cash	2,373	13,570	(29,425)
Repurchase of shares of common stock	(57,633)	(20,051)	(3,736)
Payment of common stock dividends	(16,841)	(14,423)	(10,866)
Repayment of leasehold financing	(1,351)	(1,322)	(1,301)
Proceeds from exercise of stock options	2,160	4,287	6,943
Reduction of (increase in) income taxes paid due to the tax benefit (expense) from employee stock option expense	135	(303)	3,730
Net cash used for financing activities	(71,157)	(18,242)	(34,655)
Net increase (decrease) in cash and cash equivalents	16,049	(35,775)	25,232
Cash and cash equivalents at beginning of year	24,369	60,144	34,912
Cash and cash equivalents at end of year	40,418	24,369	60,144
Supplemental disclosures of cash flow information:
Interest paid	73	91	110
Income taxes paid	7,367	13,744	24,079
Non-cash transactions:
Issuance of stock for 401K match			$ 220