UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES:
Net income	$ 607,210	$ 455,623
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	56,540	40,412
Amortization	46,550	43,018
Provision for uncollectible accounts	28,331	13,530
Deferred income tax expense (benefit)	8,654	(24,441)
Net unrealized gains on marketable equity securities	(54,514)	0
Stock-based compensation expense and other stock-based payments	71,500	59,059
Amortization of debt issuance costs	2,113	2,067
Amortization of debt discount	15,127	17,625
Changes in assets and liabilities:
Accounts receivable	(96,034)	(78,428)
Prepaid expenses and other current assets	(708,925)	(443,643)
Accounts payable, accrued expenses and other current liabilities	631,496	305,758
Other	32,327	(9,962)
Net cash provided by operating activities	640,375	380,618
INVESTING ACTIVITIES:
Purchase of investments	(713,748)	(1,498,723)
Proceeds from sale of investments	2,481,251	676,474
Additions to property and equipment	(131,987)	(70,559)
Acquisitions and other investments, net of cash acquired	0	(6)
Net cash provided by (used in) investing activities	1,635,516	(892,814)
FINANCING ACTIVITIES:
Proceeds from the issuance of long-term debt	0	1,051,722
Payments for conversion of senior notes	(1,487,109)	(4)
Payment of debt	(348)	0
Payments for repurchase of common stock	(718,941)	(209,797)
Proceeds from exercise of stock options	1,161	1,479
Net cash (used in) provided by financing activities	(2,205,237)	843,400
Effect of exchange rate changes on cash, cash equivalents and restricted cash and cash equivalents	10,599	21,737
Net increase in cash, cash equivalents and restricted cash and cash equivalents	81,253	352,941
Cash, cash equivalents and restricted cash and cash equivalents, beginning of period	2,563,341	2,082,007
Cash, cash equivalents and restricted cash and cash equivalents, end of period	2,644,594	2,434,948
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for income taxes	783,974	536,192
Cash paid during the period for interest	74,275	38,496
Non-cash financing activity	$ 0	$ 1,000