Summary of Significant Accounting Policies - PAC - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) operatingSegment reportableSegment	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Number of reportable segments | operatingSegment	8
PAC
Debt Securities, Available-for-sale [Line Items]
Accumulated unrealized gains and losses on available-for-sale securities	$ 0	$ 0
Unbilled contracts receivable	$ 296	$ 301
Number of reportable segments | reportableSegment	1