CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities:
Net income	$ 198	$ 107
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	25	37
Deferred income taxes	15	(6)
Share-based compensation	9	6
Non-cash restructuring costs	0	17
Amortization of convertible senior notes and finance lease liabilities	3	7
(Gain) loss on debt extinguishment	(3)	10
Other, net	3	2
Changes in operating assets and liabilities:
Receivables	(29)	(83)
Prepaid expenses and other current assets	20	(239)
Medical claims and benefits payable	34	(163)
Amounts due government agencies	(35)	172
Accounts payable and accrued liabilities	(30)	319
Deferred revenue	(4)	130
Income taxes	43	78
Net cash provided by operating activities	249	394
Investing activities:
Purchases of investments	(185)	(389)
Proceeds from sales and maturities of investments	366	543
Purchases of property, equipment and capitalized software	(6)	(4)
Other, net	(4)	(5)
Net cash provided by investing activities	171	145
Financing activities:
Repayment of principal amount of 1.125% Convertible Notes	(46)	0
Cash paid for partial settlement of 1.125% Conversion Option	(115)	0
Cash received for partial termination of 1.125% Call Option	115	0
Cash paid for partial termination of 1.125% Warrants	(103)	0
Proceeds from borrowings under Term Loan	100	0
Other, net	1	(5)
Net cash used in financing activities	(48)	(5)
Net increase in cash, cash equivalents, and restricted cash and cash equivalents	372	534
Cash, cash equivalents, and restricted cash and cash equivalents at beginning of period	2,926	3,290
Cash, cash equivalents, and restricted cash and cash equivalents at end of period	3,298	3,824
Schedule of non-cash investing and financing activities:
Common stock used for share-based compensation	(7)	(5)
Details of change in fair value of derivatives, net:
Change in fair value of derivatives, net	0	0
1.625% Convertible Notes exchange transaction:
Common stock issued in exchange for 1.625% Convertible Notes	0	131
Component allocated to additional paid-in capital, net of income taxes	0	(23)
Net increase to additional paid-in capital	0	108
1.125% Call Option
Details of change in fair value of derivatives, net:
Change in fair value of derivatives, net	155	63
1.125% Conversion Option
Financing activities:
Cash received for partial termination of 1.125% Call Option	115
Details of change in fair value of derivatives, net:
Change in fair value of derivatives, net	$ (155)	$ (63)