Redeemable Convertible Preferred Stock - Schedule of Redeemable Convertible Preferred Stock Outstanding (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 30, 2025	Jun. 20, 2025	Apr. 01, 2025	Mar. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)		787,439,505			764,600,000
Temporary equity, issued (in shares)		751,145,116			734,142,041
Temporary equity outstanding (in shares)		751,145,116		734,142,041	734,142,041	734,142,041	734,142,041	734,142,041
Aggregate Liquidation Preference		$ 1,946,409			$ 1,781,762
Net Carrying Value	$ 0	$ 2,446,382		$ 2,246,113	$ 2,221,651	$ 2,171,991	$ 2,148,397	$ 2,125,284
Series A Preferred Stock
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)	0	490,000,000			490,000,000
Temporary equity, issued (in shares)	0	485,795,293			485,795,293
Temporary equity outstanding (in shares)	0	485,795,293			485,795,293
Original issue price per share (in dollars per share)		$ 0.61			$ 0.61
Aggregate Liquidation Preference		$ 296,335			$ 296,335
Net Carrying Value	$ 0	$ 709,261			$ 709,261
Series B Preferred Stock
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)	0	30,000,000			30,000,000
Temporary equity, issued (in shares)	0	29,629,630			29,629,630
Temporary equity outstanding (in shares)	0	29,629,630			29,629,630
Original issue price per share (in dollars per share)		$ 0.54			$ 0.54
Aggregate Liquidation Preference		$ 16,000			$ 16,000
Net Carrying Value	$ 0	$ 42,963			$ 42,963
Series C Preferred Stock
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)	0	142,000,000			142,000,000
Temporary equity, issued (in shares)	0	116,200,835			116,200,835
Temporary equity outstanding (in shares)	0	116,200,835			116,200,835
Original issue price per share (in dollars per share)		$ 2.76	$ 4.58	$ 2.76	$ 2.76
Aggregate Liquidation Preference		$ 415,616			$ 408,715
Net Carrying Value	$ 0	$ 415,616			$ 408,715
Series D Preferred Stock
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)	0	102,600,000			102,600,000
Temporary equity, issued (in shares)	0	102,516,283			102,516,283
Temporary equity outstanding (in shares)	0	102,516,283			102,516,283
Original issue price per share (in dollars per share)		$ 8.10			$ 8.10
Aggregate Liquidation Preference		$ 1,078,273			$ 1,060,712
Net Carrying Value	$ 0	$ 1,078,273			$ 1,060,712
Series E Preferred Stock
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)		12,345,678
Temporary equity, issued (in shares)		12,345,674
Temporary equity outstanding (in shares)		12,345,674
Original issue price per share (in dollars per share)		$ 8.10
Aggregate Liquidation Preference		$ 101,786
Net Carrying Value		$ 145,412
Series F Preferred Stock
Temporary Equity [Line Items]
Temporary equity, authorized (in shares)		10,493,827
Temporary equity, issued (in shares)		4,657,401
Temporary equity outstanding (in shares)		4,657,401
Original issue price per share (in dollars per share)		$ 8.10
Aggregate Liquidation Preference		$ 38,399
Net Carrying Value		$ 54,857