Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Mar. 31, 2024
Class of Stock [Line Items]
Common stock share value	$ 8	$ 142	$ 228
Sale of stock, number of shares issued in transaction (in shares)		13.6
Sale of stock, price per share (in dollars per share)		$ 11.00
Sale of stock, consideration received on transaction		$ 150
At-the-Market Facility
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	0.6
Sale of stock, consideration received on transaction	$ 8
Third Stock Purchase Agreement Amendment
Class of Stock [Line Items]
Contract with customer, asset, before allowance for credit loss			228
Capitalized contract cost, gross			$ 5
Gilead
Class of Stock [Line Items]
Sale of stock, consideration received on transaction		$ 15
Gilead | Third Stock Purchase Agreement Amendment
Class of Stock [Line Items]
Common stock shares issued (in shares)			15.2
Shares issued, price per share (in dollars per share)			$ 21.00
Common stock share value			$ 320
Premiums earned, net			$ 87
Gilead
Class of Stock [Line Items]
Sale of stock, number of shares acquired in transaction (in shares)		1.4