Income Taxes (Summary of Deductible Loss and Credit Carryforwards) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Investments Owned Federal Income Tax Note [Line Items]
Loss and Credit Carryforwards, Deductible Amount	$ 1,411
Loss and Credit Carryforwards, Deferred Tax Asset	223
Federal
Investments Owned Federal Income Tax Note [Line Items]
Loss Carryforwards, Deductible Amount	533
Loss Carryforwards, Deferred Tax Asset	$ 112
Loss Carryforwards, Expiration Period	2037
Federal | Production and Other Credits
Investments Owned Federal Income Tax Note [Line Items]
Credit Carryforwards, Deductible Amount	$ 0
Credit Carryforwards, Deferred Tax Asset	$ 30
Federal | Minimum [Member] | Production and Other Credits
Investments Owned Federal Income Tax Note [Line Items]
Credit Carryforwards, Expiration Period	2041
Federal | Maximum [Member] | Production and Other Credits
Investments Owned Federal Income Tax Note [Line Items]
Credit Carryforwards, Expiration Period	2043
State
Investments Owned Federal Income Tax Note [Line Items]
Loss Carryforwards, Deductible Amount	$ 878
Loss Carryforwards, Deferred Tax Asset	44
State | Investment and Other Credits
Investments Owned Federal Income Tax Note [Line Items]
Credit Carryforwards, Deductible Amount	0
Credit Carryforwards, Deferred Tax Asset	$ 37
State | Minimum [Member]
Investments Owned Federal Income Tax Note [Line Items]
Loss Carryforwards, Expiration Period	2037
State | Minimum [Member] | Investment and Other Credits
Investments Owned Federal Income Tax Note [Line Items]
Credit Carryforwards, Expiration Period	2026
State | Maximum [Member]
Investments Owned Federal Income Tax Note [Line Items]
Loss Carryforwards, Expiration Period	2042
State | Maximum [Member] | Investment and Other Credits
Investments Owned Federal Income Tax Note [Line Items]
Credit Carryforwards, Expiration Period	2031