Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 1,036,455	$ 313,382
Marketable securities	855,650	398,554
Accounts receivable, net of reserves of $1,534 and $1,281 at December 31, 2018 and 2017, respectively	479,889	461,457
Prepaid expenses and other current assets	163,360	172,853
Total current assets	2,535,354	1,346,246
Property and equipment, net	910,618	862,535
Marketable securities	209,066	567,592
Goodwill	1,487,404	1,498,688
Acquired intangible assets, net	168,348	201,259
Deferred income tax assets	34,913	36,231
Other assets	116,067	136,365
Total assets	5,461,770	4,648,916
Current liabilities:
Accounts payable	99,089	80,278
Accrued expenses	328,304	283,743
Deferred revenue	69,083	70,495
Convertible senior notes	686,552	0
Other current liabilities	27,681	22,178
Total current liabilities	1,210,709	456,694
Deferred revenue	4,557	6,062
Deferred income tax liabilities	19,624	17,823
Convertible senior notes	874,080	662,913
Other liabilities	160,940	142,955
Total liabilities	2,269,910	1,286,447
Commitments and contingencies (Note 12)
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; 162,904,550 and 169,893,324 shares issued and outstanding at December 31, 2018 and 2017, respectively	1,629	1,699
Additional paid-in capital	3,670,033	4,073,362
Accumulated other comprehensive loss	(48,912)	(21,930)
Accumulated deficit	(430,890)	(690,662)
Total stockholders’ equity	3,191,860	3,362,469
Total liabilities and stockholders’ equity	$ 5,461,770	$ 4,648,916