Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 144,946	$ 145,686
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	144,449	112,228
Stock-based compensation	61,920	56,792
Excess tax benefits from stock-based compensation	(22,737)	(19,661)
(Benefit) provision for deferred income taxes	(16,275)	21,840
Amortization of debt discount and issuance costs	9,253	6,457
Other non-cash reconciling items, net	1,146	1,195
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(14,292)	(41,254)
Prepaid expenses and other current assets	12,022	(12,998)
Accounts payable and accrued expenses	31,673	21,459
Deferred revenue	7,023	4,750
Other current liabilities	199	1,419
Other non-current assets and liabilities	4,425	(8,666)
Net cash provided by operating activities	363,752	289,247
Cash flows from investing activities:
Cash paid for acquired businesses, net of cash acquired	(122,945)	(386,532)
Purchases of property and equipment	(159,495)	(97,992)
Capitalization of internal-use software development costs	(73,587)	(56,533)
Purchases of short- and long-term marketable securities	(405,989)	(863,591)
Proceeds from sales of short- and long-term marketable securities	2,008	354,313
Proceeds from maturities of short- and long-term marketable securities	527,677	183,809
Other non-current assets and liabilities	(1,909)	2,028
Net cash used in investing activities	(234,240)	(864,498)
Cash flows from financing activities:
Proceeds from the issuance of convertible senior notes, net of issuance costs	0	678,735
Proceeds from the issuance of warrants related to convertible senior notes	0	77,970
Purchase of note hedge related to convertible senior notes	0	(101,292)
Repayment of acquired debt and capital leases	0	(17,862)
Proceeds related to the issuance of common stock under stock plans	36,512	57,999
Excess tax benefits from stock-based compensation	22,737	19,661
Employee taxes paid related to net share settlement of stock-based awards	(39,354)	(34,248)
Repurchases of common stock	(126,068)	(187,491)
Other non-current assets and liabilities	(1,250)	0
Net cash (used in) provided by financing activities	(107,423)	493,472
Effects of exchange rate changes on cash and cash equivalents	(3,291)	2,053
Net increase (decrease) in cash and cash equivalents	18,798	(79,726)
Cash and cash equivalents at beginning of period	238,650	333,891
Cash and cash equivalents at end of period	257,448	254,165
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net of refunds received in the six months ended June 30, 2015 of $17,964	12,055	60,360
Non-cash investing and financing activities:
Purchases of property and equipment and capitalization of internal-use software development costs included in accounts payable and accrued expenses	41,874	36,146
Capitalization of stock-based compensation	$ 8,615	$ 7,727