Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 417,393	$ 517,690
Short-term investments	2,892,917	1,520,180
Prepaid expenses and other current assets	367,487	282,572
Total current assets	3,677,797	2,320,442
Restricted cash and cash equivalents	122,983	187,374
Restricted investments	1,165,299	863,713
Property and equipment, net	138,149	109,257
Operating lease right of use assets	347,027
Intangible assets, net	99,612	117,733
Goodwill	150,926	152,085
Other assets	2,683	9,439
Total assets	5,704,476	3,760,043
Current liabilities
Accounts payable	12,690	32,343
Insurance reserves	1,207,380	810,273
Accrued and other current liabilities	813,288	606,203
Operating lease liabilities — current	92,458
Total current liabilities	2,125,816	1,448,819
Operating lease liabilities	295,164
Other liabilities	6,364	30,458
Total liabilities	2,427,344	1,479,277
Commitments and contingencies (Note 6)
Redeemable convertible preferred stock, $0.00001 par value; no and 227,328,900 shares authorized as of June 30, 2019 and December 31, 2018, respectively; no and 219,175,709 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	0	5,152,047
Stockholders’ equity (deficit)
Preferred stock, $0.00001 par value; 1,000,000,000 and no shares authorized as of June 30, 2019 and December 31, 2018, respectively; no shares issued and outstanding as of June 30, 2019 and December 31, 2018	0	0
Common stock, $0.00001 par value; 18,000,000,000 Class A shares and 340,000,000 shares authorized, 279,970,833 Class A shares and 22,438,472 shares issued and outstanding, as of June 30, 2019 and December 31, 2018, respectively; 100,000,000 and no Class B shares authorized, 12,779,709 and no Class B shares issued and outstanding, as of June 30, 2019 and December 31, 2018, respectively	3
Additional paid-in capital	7,999,678	73,916
Accumulated other comprehensive income	5,493	133
Accumulated deficit	(4,728,042)	(2,945,330)
Total stockholders’ equity (deficit)	3,277,132	(2,871,281)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	$ 5,704,476	$ 3,760,043