CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 863,620	$ 649,666
Marketable securities	839,470	1,063,679
Accounts receivable, net of allowances of $5,612 and $2,851 as of June 30, 2020 and December 31, 2019, respectively	209,933	316,367
Prepaid expenses and other current assets	45,170	37,522
Total current assets	1,958,193	2,067,234
Property and equipment, net	83,006	91,992
Operating lease right-of-use assets	165,250	188,251
Goodwill and intangible assets, net	14,067	14,576
Restricted cash	23,221	25,339
Other assets	5,887	5,925
Total assets	2,249,624	2,393,317
Current liabilities:
Accounts payable	43,705	34,334
Accrued expenses and other current liabilities	122,912	141,823
Total current liabilities	166,617	176,157
Operating lease liabilities	151,282	173,392
Other liabilities	25,095	20,063
Total liabilities	342,994	369,612
Commitments and contingencies
Stockholders’ equity:
Common stock	6	6
Additional paid-in capital	4,351,557	4,229,778
Accumulated other comprehensive income	3,737	647
Accumulated deficit	(2,448,670)	(2,206,726)
Total stockholders’ equity	1,906,630	2,023,705
Total liabilities and stockholders’ equity	$ 2,249,624	$ 2,393,317