Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 44,669	$ 29,923	$ 24,981
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	18,294	17,345	15,671
Provision for doubtful accounts	648	443	1
Stock compensation	4,016	3,471	2,708
Loss (gain) on disposal of property and equipment	(42)	338	0
Gain on sale of assets	(14,242)	0	0
Bond premium amortization	1,294	1,092	2,530
Cash provided (used) by changes in operating assets and liabilities
Accounts receivable	6,232	(6,378)	(6,501)
Inventories	3,170	(3,670)	2,012
Prepaid expenses and other assets	(920)	(2,518)	(3,150)
Accounts payable	2,673	(8,222)	10,380
Accrued liabilities	1,684	1,946	(2,046)
Deferred revenue	(254)	(2,135)	2,389
Prepaid and deferred income taxes	(2,735)	1,460	2,164
Net cash provided by operating activities	64,487	33,095	51,139
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(15,824)	(23,171)	(16,690)
Proceeds from Sale of Assets	16,201	893	0
Proceeds from insurance	2,781	622	0
Assets purchased	0	0	(29,447)
Business acquisition, net of assets acquired	0	0	(5,662)
Change in restricted cash	0	0	6,014
Purchases of investment securities	(90,502)	(23,382)	(99,185)
Proceeds from sale of investment securities	41,610	64,670	107,211
Net cash provided (used) by investing activities	(45,734)	19,632	(37,759)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from exercise of stock options	7,974	2,517	1,375
Proceeds from employee stock purchase plan	1,828	1,576	1,271
Tax benefits from exercise of stock options	4,288	1,680	101
Purchase of treasury stock	(11,956)	(28,648)	(20,441)
Net cash provided (used) by financing activities	2,134	(22,875)	(17,694)
Effect of exchange rate changes on cash	(147)	(2,250)	(134)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	20,740	27,602	(4,448)
CASH AND CASH EQUIVALENTS, beginning of period	78,850	51,248	55,696
CASH AND CASH EQUIVALENTS, end of period	99,590	78,850	51,248
SUPPLEMENTAL DISCLSOURE OF CASH FLOW INFORMATION
Cash paid during the year for income taxes	20,110	15,249	9,034
NON-CASH INVESTING ACTIVITIES
Accrued liabilities for property and equipment	$ 418	$ 716	$ 0