Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Statement of Cash Flows [Abstract]
Net income	$ 95,439	$ 79,750
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,766	5,981
Amortization of debt issuance costs	91	91
Stock-based compensation	3,051	2,935
Deferred compensation	0	19
(Gain) loss on disposal of fixed assets	(2)	69
Deferred income taxes	3,061	(1,790)
Tax benefit from exercise of stock options	0	(1,551)
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	0
Provision for legal settlement	32,000	0
Payment of class action legal settlement	(32,000)	0
Effect of changes in operating assets and liabilities:
Receivables	(12,282)	2,178
Inventories	8,257	(8,282)
Prepaid expenses and other assets	(2,066)	(3)
Accounts payable	4,055	4,387
Other liabilities	5,158	10,263
Net cash provided by operating activities	111,528	94,047
Cash flows from investing activities:
Capital expenditures	(17,901)	(5,374)
Restricted cash	(308)	0
Proceeds from the sale of fixed assets	15	0
Net cash used in investing activities	(18,194)	(5,374)
Cash flows from financing activities:
Principal payments on long-term debt	(2,970)	(2,970)
Proceeds from exercise of stock options	1,805	1,910
Tax benefit from exercise of stock options	0	1,551
Net cash (used in) provided by financing activities	(1,165)	491
Effect of exchange rate changes on cash and cash equivalents	(60)	0
Net increase in cash and cash equivalents	92,109	89,164
Cash and cash equivalents at beginning of period	224,253	95,788
Cash and cash equivalents at end of period	$ 316,362	$ 184,952