CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 4,865	$ 4,202
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	1,291	1,246
Provisions for contracts, inventory and accounts receivable reserves	32	949
Amortization of bond premium	470	769
Stock compensation expense	308	258
Changes in assets and liabilities:
Accounts receivable	3,139	(1,153)
Unbilled costs and fees	(355)	(5,313)
Inventories	(2,287)	387
Prepaid expenses and other assets	1,959	2,333
Accounts payable	633	(302)
Accrued income taxes	844
Customer deposits	4,766	2,469
Deferred revenue	(1,373)	(1,733)
Accrued expenses and other liabilities	(2,666)	(1,028)
Net cash provided by operating activities	11,626	3,084
Cash flows from investing activities:
Purchases of short-term investments		(31,513)
Proceeds from sales and maturities of short-term investments	47,638	37,341
Purchases of property and equipment, net	(707)	(1,114)
Net cash provided by investing activities	46,931	4,714
Cash flows from financing activities:
(Increase) decrease in restricted cash and investments	(1,797)	1,477
Proceeds from exercise of stock options	1,452	112
Repurchase of shares of common stock	(12,306)	(19,591)
Repayment of leasehold financing liability	(369)	(333)
Payment of common stock dividend	(3,893)	(4,474)
Net cash used for financing activities	(16,913)	(22,809)
Net increase (decrease) in cash and cash equivalents	41,644	(15,011)
Cash and cash equivalents at beginning of period	40,418	24,369
Cash and cash equivalents at end of period	$ 82,062	$ 9,358