UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES:
Net income	$ 455,623	$ 374,424
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	40,412	30,486
Amortization	43,018	42,385
Provision for uncollectible accounts, net	13,530	6,812
Deferred income tax benefit	(24,441)	(25,681)
Stock-based compensation expense and other stock-based payments	59,059	66,034
Amortization of debt issuance costs	2,067	1,837
Amortization of debt discount	17,625	17,009
Impairment of cost-method investment	0	50,350
Excess tax benefits on stock-based awards and other equity deductions	0	18,073
Changes in assets and liabilities:
Accounts receivable	(78,428)	(191,704)
Prepaid expenses and other current assets	(443,643)	(340,485)
Accounts payable, accrued expenses and other current liabilities	305,758	294,349
Other	(9,962)	869
Net cash provided by operating activities	380,618	344,758
INVESTING ACTIVITIES:
Purchase of investments	(1,498,723)	(1,051,346)
Proceeds from sale of investments	676,474	1,252,604
Additions to property and equipment	(70,559)	(53,256)
Acquisitions and other investments, net of cash acquired	(6)	(723)
Net cash (used in) provided by investing activities	(892,814)	147,279
FINANCING ACTIVITIES:
Proceeds from short-term borrowing	0	100,000
Proceeds from the issuance of long-term debt	1,051,722	2,500
Payments related to conversion of senior notes	(4)	0
Payments for repurchase of common stock	(209,797)	(241,719)
Proceeds from exercise of stock options	1,479	4,815
Net cash provided by (used in) financing activities	843,400	(134,404)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	21,737	22,296
Net increase in cash, cash equivalents and restricted cash	352,941	379,929
Cash, cash equivalents and restricted cash, beginning of period	2,082,007	1,478,071
Cash, cash equivalents and restricted cash, end of period	2,434,948	1,858,000
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for income taxes	536,192	449,314
Cash paid during the period for interest	38,496	40,119
Non-cash financing activity	$ 1,000	$ 0