CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 581,068	$ 352,917
Marketable securities	835,420	745,156
Accounts receivable, net of reserves of $1,947 and $1,822 at June 30, 2021, and December 31, 2020, respectively	656,609	660,052
Prepaid expenses and other current assets	180,155	171,406
Total current assets	2,253,252	1,929,531
Marketable securities	1,164,620	1,398,802
Property and equipment, net	1,538,422	1,478,272
Operating lease right-of-use assets	830,022	793,945
Acquired intangible assets, net	217,519	234,724
Goodwill	1,685,859	1,674,371
Deferred income tax assets	99,634	106,918
Other assets	131,610	147,567
Total assets	7,920,938	7,764,130
Current liabilities:
Accounts payable	93,465	118,546
Accrued expenses	289,189	380,468
Deferred revenue	95,216	76,600
Operating lease liabilities	158,390	154,801
Other current liabilities	11,189	27,755
Total current liabilities	647,449	758,170
Deferred revenue	4,623	5,262
Deferred income tax liabilities	36,124	37,458
Convertible senior notes	1,941,113	1,906,707
Operating lease liabilities	733,523	715,404
Other liabilities	81,449	89,833
Total liabilities	3,444,281	3,512,834
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; 164,481,023 shares issued and 163,018,768 shares outstanding at June 30, 2021, and 162,709,720 shares issued and outstanding at December 31, 2020	1,645	1,627
Additional paid-in capital	3,743,743	3,664,820
Accumulated other comprehensive loss	(31,557)	(20,201)
Treasury stock, at cost, 1,462,255 shares at June 30, 2021, and no shares at December 31, 2020	(154,416)	0
Retained earnings	917,242	605,050
Total stockholders’ equity	4,476,657	4,251,296
Total liabilities and stockholders’ equity	$ 7,920,938	$ 7,764,130