Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 705,407	$ 313,382
Marketable securities	1,096,233	398,554
Accounts receivable, net of reserves of $1,358 and $1,281 at September 30, 2018, and December 31, 2017, respectively	466,364	461,457
Prepaid expenses and other current assets	161,785	172,853
Total current assets	2,429,789	1,346,246
Property and equipment, net	884,483	862,535
Marketable securities	257,135	567,592
Goodwill	1,488,868	1,498,688
Acquired intangible assets, net	176,640	201,259
Deferred income tax assets	23,688	36,231
Other assets	103,284	136,365
Total assets	5,363,887	4,648,916
Current liabilities:
Accounts payable	96,051	80,278
Accrued expenses	305,267	283,743
Deferred revenue	93,732	70,495
Convertible senior notes	680,564	0
Other current liabilities	20,324	22,178
Total current liabilities	1,195,938	456,694
Deferred revenue	5,218	6,062
Deferred income tax liabilities	18,827	17,823
Convertible senior notes	864,679	662,913
Other liabilities	123,695	142,955
Total liabilities	2,208,357	1,286,447
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.01 par value; 5,000,000 shares authorized; 700,000 shares designated as Series A Junior Participating Preferred Stock; no shares issued or outstanding	0	0
Common stock, $0.01 par value; 700,000,000 shares authorized; 172,234,085 shares issued and 163,886,719 shares outstanding at September 30, 2018, and 169,893,324 shares issued and outstanding at December 31, 2017	1,722	1,699
Additional paid-in capital	4,352,857	4,073,362
Accumulated other comprehensive loss	(48,218)	(21,930)
Treasury stock, at cost, 8,347,366 shares at September 30, 2018, and no shares at December 31, 2017	(625,925)	0
Accumulated deficit	(524,906)	(690,662)
Total stockholders’ equity	3,155,530	3,362,469
Total liabilities and stockholders’ equity	$ 5,363,887	$ 4,648,916