Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 329,515	$ 517,690
Short-term investments	705,371	1,520,180
Prepaid expenses and other current assets	345,526	282,572
Total current assets	1,380,412	2,320,442
Restricted cash and cash equivalents	172,506	187,374
Restricted investments	993,335	863,713
Property and equipment, net	120,473	109,257
Operating lease right of use assets	304,605
Intangible assets, net	108,572	117,733
Goodwill	150,650	152,085
Other assets	10,354	9,439
Total assets	3,240,907	3,760,043
Current liabilities
Accounts payable	39,394	32,343
Insurance reserves	936,984	810,273
Accrued and other current liabilities	702,009	606,203
Operating lease liabilities — current	73,676
Total current liabilities	1,752,063	1,448,819
Operating lease liabilities	263,755
Other liabilities	4,660	30,458
Total liabilities	2,020,478	1,479,277
Commitments and contingencies (Note 6)
Redeemable convertible preferred stock, $0.00001 par value, 227,328,900 shares authorized as of March 31, 2019 and December 31, 2018; 219,175,709 issued and outstanding as of March 31, 2019 and December 31, 2018	5,152,047	5,152,047
Stockholders’ deficit
Additional paid-in capital	149,999	73,916
Accumulated other comprehensive income	2,186	133
Accumulated deficit	(4,083,803)	(2,945,330)
Total stockholders’ deficit	(3,931,618)	(2,871,281)
Total liabilities, redeemable convertible preferred stock and stockholders’ deficit	$ 3,240,907	$ 3,760,043