Derivative Financial Instruments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Stockholders' equity attributable to parent	$ 2,718	$ 2,201	$ 1,788	$ 1,570
Amount of gain (loss), net of tax, to be reclassified during the next 12 months	(1)
Right to claim cash	66	114
Right to reclaim cash, cash collateral	28	84
Right to reclaim cash, maintenance margin	38	30
Obligation to return cash	12
Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Right to claim cash	14	14
Obligation to return cash	1
Derivatives designated as hedging instruments | Other assets
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	85
Custodial deposits
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) reclassified from AOCI into income	(4)	(2)
AFS securities
Derivative Instruments, Gain (Loss) [Line Items]
Loss on fair value hedge	4	2
Interest rate swaps on AFS securities
Derivative Instruments, Gain (Loss) [Line Items]
Amount representing designated last of layer	1,000	1,600
Amortized cost basis of hedge designated last of layer	1,000	1,600
Interest rate swaps on AFS securities | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Cumulative amount of fair value hedging adjustment included in the carrying amount	(5)	6
Amount representing designated last of layer	435	450
Right to claim cash	4	5
Obligation to return cash	1
Interest rate swaps on AFS securities | Derivatives designated as hedging instruments | Other assets
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	85
Interest rate swaps on AFS securities | Carrying Value | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of hedged securities	1,000	1,700
Interest rate swaps on HFI residential first mortgages | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of hedged securities	175
Cumulative amount of fair value hedging adjustment included in the carrying amount	1
Right to claim cash	1	1
Interest rate swaps on HFI residential first mortgages | Derivatives designated as hedging instruments | Other assets
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	100
Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Stockholders' equity attributable to parent	20	(5)	0	$ 0
Amount of gain (loss) reclassified from AOCI into income	$ (4)	$ (2)	$ 0