CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands	6 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 12,544	$ 21,470
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,924	2,396
Provisions for contracts, inventory and accounts receivable reserves	1,264	465
Amortization of bond premium	1,212	1,041
Deferred income taxes	1,170	1,155
Other	(24)	(122)
Stock compensation expense	1,204	2,563
Changes in assets and liabilities:
Accounts receivable	3,059	(6,698)
Unbilled costs and fees	6,800	(13,289)
Inventories	(2,050)	(7,005)
Prepaid expenses and other assets	(2,845)	2,724
Accounts payable	(1,580)	5,826
Accrued income taxes	(1,517)	(3,413)
Customer deposits	9,264	(2,438)
Deferred revenue	2,425	(572)
Accrued expenses and other liabilities	(8,435)	(1,848)
Net cash provided by operating activities	25,415	2,255
Cash flows from investing activities:
Purchases of short-term investments	(148,921)	(99,224)
Proceeds from sales and maturities of short-term investments	95,518	127,695
Purchases of property and equipment, net	(2,980)	(2,899)
Net cash (used for) provided by investing activities	(56,383)	25,572
Cash flows from financing activities:
Decrease in restricted cash and investments	14,939
Proceeds from exercise of stock options	2,835	366
Repurchase of shares of common stock	(15,923)	(3,381)
Repayment of leasehold financing	(659)	(649)
Payment of common stock dividend	(5,505)	(5,415)
Reduction of income taxes paid due to the tax benefit from employee stock option expense	131	526
Net cash used for financing activities	(4,182)	(8,553)
Net (decrease) increase in cash and cash equivalents	(35,150)	19,274
Cash and cash equivalents at beginning of period	60,144	34,912
Cash and cash equivalents at end of period	$ 24,994	$ 54,186