Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 26,827	$ 20,943
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,687	12,796
Provision for doubtful accounts	509	154
Stock compensation	2,998	2,568
Loss (gain) on disposal of property and equipment	(57)	449
Bond premium amortization	801	1,145
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	1,575	(7,763)
Inventories	1,143	(2,670)
Prepaid expenses and other assets	(2,406)	(1,874)
Accounts payable	(272)	(6,365)
Accrued liabilities	(1,698)	1,381
Deferred revenue	(254)	(2,013)
Prepaid and deferred income taxes	(6,802)	69
Net cash provided by operating activities	36,051	18,820
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(13,761)	(17,751)
Proceeds from sale of asset	0	893
Proceeds from insurance	2,781	622
Purchases of investment securities	(66,330)	(20,853)
Proceeds from sale of investment securities	26,935	60,370
Net cash provided (used) by investing activities	(50,375)	23,281
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	7,021	903
Proceeds from employee stock purchase plan	909	1,576
Tax benefits from exercise of stock options	3,682	708
Purchase of treasury stock	(9,992)	(28,648)
Net cash provided (used) by financing activities	1,620	(25,461)
Effect of exchange rate changes on cash	793	(2,217)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(11,911)	14,423
CASH AND CASH EQUIVALENTS, beginning of period	78,850	51,248
CASH AND CASH EQUIVALENTS, end of period	66,939	65,671
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 557	$ 11