CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net income	$ 20,079	$ 33,252
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,293	3,660
Provisions for contracts, inventory and accounts receivable reserves	2,746	879
Amortization of bond premium	1,895	1,581
Deferred income taxes	1,559	(73)
Other	(24)	(122)
Stock compensation expense	1,459	3,971
Changes in assets and liabilities:
Accounts receivable	10,117	1,997
Unbilled costs and fees	13,497	(14,232)
Inventories	(1,663)	(5,519)
Prepaid expenses and other assets	(2,212)	986
Accounts payable	(803)	1,491
Accrued income taxes	(52)	(4,203)
Customer deposits	8,208	(7,397)
Deferred revenue	(1,922)	2,527
Accrued expenses and other liabilities	(5,687)	519
Net cash provided by operating activities	51,490	19,317
Cash flows from investing activities:
Purchases of short-term investments	(217,785)	(114,801)
Proceeds from sales and maturities of short-term investments	151,937	149,222
Purchases of property and equipment, net	(3,751)	(4,098)
Net cash (used for) provided by investing activities	(69,599)	30,323
Cash flows from financing activities:
Decrease (increase) in restricted cash and investments	15,830	(28,485)
Proceeds from exercise of stock options	2,835	3,739
Repurchase of shares of common stock	(20,050)	(3,736)
Repayment of leasehold financing	(990)	(975)
Payment of common stock dividend	(9,964)	(8,129)
Change in income taxes paid due to the tax benefit from employee stock option expense	(201)	1,106
Net cash used for financing activities	(12,540)	(36,480)
Net (decrease) increase in cash and cash equivalents	(30,649)	13,160
Cash and cash equivalents at beginning of period	60,144	34,912
Cash and cash equivalents at end of period	$ 29,495	$ 48,072