Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 53,102	$ 50,935	$ 44,323
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	19,490	15,797	14,791
Stock-based compensation	8,707	10,477	8,838
Provision for doubtful accounts	3,198	2,178	921
Tax benefit from exercise of stock options	(95)	(121)	(231)
Deferred income tax provision	3,247	2,244	1,992
(Increase) decrease in, net of effects of acquisitions:
Accounts receivable	(13,245)	2,730	(7,149)
Inventories	2,083	(735)	(16,522)
Prepaid expenses and other current assets	99	(6,131)	(1,532)
Deferred customer acquisition costs	(8,333)	(1,452)
Other assets	1,176	1,023	1,417
Increase (decrease) in, net of effects of acquisitions:
Accounts payable	3,054	(71)	944
Accrued expenses	921	2,238	564
Income taxes payable	(867)	426	(366)
Deferred tuition revenue	(3,043)	(7,306)	1,826
Deferred revenue	26,139	1,050
Deferred rent	2,707	(92)	455
Gift certificate liability	773	1,336	1,483
Net cash provided by operating activities	99,113	74,526	51,754
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(29,783)	(13,560)	(7,022)
Acquisitions, net of cash acquired		(194,276)
Post-closing working capital adjustment related to acquisitions	3,614		3,895
Net cash used in investing activities	(26,169)	(207,836)	(3,127)
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchase of treasury shares	(35,901)	(12,455)	(6,621)
Proceeds from long-term debt		175,000
Payments for long-term debt	(26,500)	(25,000)	(35,500)
Payments of debt issuance costs		(4,978)	(156)
Payment of contingent consideration		(1,500)
Tax benefit from exercise of stock options	95	121	231
Proceeds from share option exercises	577	2,678	1,759
Net cash provided by (used in) financing activities	(61,729)	133,866	(40,287)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	1,168	358	540
NET INCREASE IN CASH AND CASH EQUIVALENTS	12,383	914	8,880
CASH AND CASH EQUIVALENTS,
Beginning of year	62,645	61,731	52,851
CASH AND CASH EQUIVALENTS,
End of year	75,028	62,645	61,731
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest	4,590	1,364	1,993
Income taxes	4,712	4,126	6,001
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING ACTIVITY:
Common stock issued in a business acquisition		$ 5,660