Summary of Significant Accounting Policies - NPC - Reconciliation of Cash (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 1,591	$ 1,096
Investments and restricted cash and cash equivalents	173	127
Total cash and cash equivalents and restricted cash and cash equivalents	1,817	1,244	$ 1,445	$ 1,268
NPC
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	43	33
Investments and restricted cash and cash equivalents	17	12
Total cash and cash equivalents and restricted cash and cash equivalents	$ 60	$ 45	$ 36	$ 25