CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 216,050	$ 177,980
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,991	11,183
Gain on disposal of property and equipment	(187)	(268)
Stock-based compensation	13,439	13,142
Deferred income taxes		1,862
Effect on cash of changes in operating assets and liabilities:
Accounts receivable	(72,699)	7,441
Distributor receivables	3,279	(951)
Inventories	(11,274)	(7,793)
Prepaid expenses and other current assets	(19,646)	(11,368)
Prepaid income taxes	52,410	25,601
Accounts payable	(22,616)	(19,317)
Accrued liabilities	(14,985)	6,788
Accrued promotional allowances	15,971	14,111
Accrued distributor terminations	71	315
Accrued compensation	(18,350)	(15,802)
Income taxes payable	(1,059)	(5,506)
Other liabilities	1,108
Deferred revenue	(6,592)	(4,454)
Net cash provided by operating activities	148,911	192,964
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of available-for-sale investments	334,216	71,553
Purchases of available-for-sale investments	(247,421)	(58,314)
Purchases of property and equipment	(13,049)	(19,093)
Proceeds from sale of property and equipment	3,397	452
Decrease (Increase) in intangibles	280	(848)
Increase in other assets	(1,549)	(52)
Net cash provided by (used in) investing activities	75,874	(6,302)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on debt	(543)	(700)
Issuance of common stock	6,501	13,621
Purchases of common stock held in treasury	(251,950)	(64)
Net cash (used in) provided by financing activities	(245,992)	12,857
Effect of exchange rate changes on cash and cash equivalents	3,945	(764)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS	(17,262)	198,755
CASH AND CASH EQUIVALENTS, beginning of period	528,622	377,582
CASH AND CASH EQUIVALENTS, end of period	511,360	576,337
Cash paid during the period for:
Interest	16	19
Income taxes	$ 15,223	$ 66,094