Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 332,557	$ 238,650
Marketable securities	380,728	519,642
Accounts receivable, net of reserves of $9,966 and $9,023 at March 31, 2015, and December 31, 2014, respectively	356,629	329,578
Prepaid expenses and other current assets	130,041	128,981
Deferred income tax assets	41,624	45,704
Total current assets	1,241,579	1,262,555
Property and equipment, net	666,093	601,591
Marketable securities	801,854	869,992
Goodwill	1,064,149	1,051,294
Acquired intangible assets, net	130,532	132,412
Deferred income tax assets	1,892	1,955
Other assets	80,814	81,747
Total assets	3,986,913	4,001,546
Current liabilities:
Accounts payable	67,637	77,412
Accrued expenses	144,117	204,686
Deferred revenue	55,301	49,679
Other current liabilities	2,276	2,234
Total current liabilities	269,331	334,011
Deferred revenue	4,182	3,829
Deferred income tax liabilities	44,580	39,299
Convertible senior notes	609,647	604,851
Other liabilities	77,491	74,221
Total liabilities	1,005,231	1,056,211
Commitments and contingencies
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; 179,616,373 shares issued and 178,684,242 shares outstanding at March 31, 2015, and 178,300,603 shares issued and outstanding at December 31, 2014	1,796	1,783
Additional paid-in capital	4,587,000	4,559,430
Accumulated other comprehensive loss	(23,913)	(17,611)
Treasury stock, at cost, 932,131 shares at March 31, 2015, and no shares at December 31, 2014	(62,680)	0
Accumulated deficit	(1,520,521)	(1,598,267)
Total stockholders’ equity	2,981,682	2,945,335
Total liabilities and stockholders’ equity	$ 3,986,913	$ 4,001,546