CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 261,485	$ 216,050
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,870	13,991
Gain on disposal of property and equipment	(115)	(187)
Stock-based compensation	15,324	13,439
Deferred income taxes	472
Effect on cash of changes in operating assets and liabilities:
Accounts receivable	(116,426)	(72,699)
Distributor receivables	2,923	3,279
Inventories	(24,004)	(11,274)
Prepaid expenses and other current assets	(21,492)	(19,646)
Prepaid income taxes	(25,224)	52,410
Accounts payable	18,565	(22,616)
Accrued liabilities	(2,262)	(14,985)
Accrued promotional allowances	23,103	15,971
Accrued distributor terminations	10,272	71
Accrued compensation	(21,832)	(18,350)
Income taxes payable	(4,125)	(1,059)
Other liabilities	1,338	1,108
Deferred revenue	(9,476)	(6,592)
Net cash provided by operating activities	123,396	148,911
CASH FLOWS FROM INVESTING ACTIVITIES:
Sales of available-for-sale investments	232,387	334,216
Purchases of available-for-sale investments	(175,314)	(247,421)
Purchases of property and equipment	(8,485)	(13,049)
Proceeds from sale of property and equipment	184	3,397
Decrease in intangibles	298	280
Increase in other assets	(2,291)	(1,549)
Net cash provided by investing activities	46,779	75,874
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on debt	(393)	(543)
Issuance of common stock	35,163	6,501
Purchases of common stock held in treasury	(222,792)	(251,950)
Net cash used in financing activities	(188,022)	(245,992)
Effect of exchange rate changes on cash and cash equivalents	(1,322)	3,945
NET DECREASE IN CASH AND CASH EQUIVALENTS	(19,169)	(17,262)
CASH AND CASH EQUIVALENTS, beginning of period	637,513	528,622
CASH AND CASH EQUIVALENTS, end of period	618,344	511,360
Cash paid during the period for:
Interest	15	16
Income taxes	$ 82,002	$ 15,223