Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 248,726	$ 333,891
Marketable securities	449,404	340,005
Accounts receivable, net of reserves of $6,933 and $3,703 at March 31, 2014 and December 31, 2013, respectively	301,954	271,988
Prepaid expenses and other current assets	89,198	62,096
Deferred income tax assets	38,018	21,734
Total current assets	1,127,300	1,029,714
Property and equipment, net	503,601	450,287
Marketable securities	721,271	573,026
Goodwill	1,050,780	757,368
Acquired intangible assets, net	157,621	77,429
Deferred income tax assets	2,476	2,325
Other assets	88,443	67,536
Total assets	3,651,492	2,957,685
Current liabilities:
Accounts payable	61,707	73,710
Accrued expenses	130,447	150,385
Deferred revenue	48,359	36,952
Other current liabilities	3,673	2,119
Total current liabilities	244,186	263,166
Deferred revenue	4,181	3,199
Deferred income tax liabilities	28,445	4,737
Convertible senior notes	590,714	0
Other liabilities	71,821	57,152
Total liabilities	939,347	328,254
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; 180,494,143 shares issued and 178,517,946 shares outstanding at March 31, 2014 and 178,580,696 shares issued and outstanding at December 31, 2013	1,832	1,808
Additional paid-in capital	4,687,512	4,561,929
Accumulated other comprehensive loss	(1,637)	(2,091)
Treasury stock, at cost, 1,976,197 shares at March 31, 2014 and no shares at December 31, 2013	(116,147)	0
Accumulated deficit	(1,859,415)	(1,932,215)
Total stockholders’ equity	2,712,145	2,629,431
Total liabilities and stockholders’ equity	$ 3,651,492	$ 2,957,685