Unaudited Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Statement of Cash Flows [Abstract]
Net income	$ 73,957	$ 52,684
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	4,435	3,913
Amortization of debt issuance costs	61	61
Stock-based compensation	2,065	901
Deferred compensation	0	19
Loss on disposal of fixed assets	13	62
Deferred income taxes	12,721	(742)
Tax benefit from exercise of stock options	(36)	0
Payment of legal settlement	(32,000)	0
Effect of changes in operating assets and liabilities:
Receivables	(4,212)	11,913
Inventories	(3,923)	(2,749)
Prepaid expenses and other assets	(334)	589
Accounts payable	2,741	14,907
Other liabilities	(835)	8,050
Net cash provided by operating activities	54,653	89,608
Cash flows from investing activities:
Capital expenditures	(3,766)	(3,767)
Net cash used in investing activities	(3,766)	(3,767)
Cash flows from financing activities:
Principal payments on long-term debt	(1,980)	(1,980)
Tax benefit from exercise of stock options	36	0
Proceeds from exercise of stock options	373	43
Net cash used in financing activities	(1,571)	(1,937)
Effect of exchange rate changes on cash and cash equivalents	(14)	0
Net increase in cash and cash equivalents	49,302	83,904
Cash and cash equivalents at beginning of period	224,253	95,788
Cash and cash equivalents at end of period	$ 273,555	$ 179,692