Derivative Instruments and Hedging Activities (Notional and Recorded Fair Values) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023
Derivative [Line Items]
Notional amount	$ 22,342	$ 22,148
Other assets	481	420
Other liabilities	388	333
Net credit valuation adjustment reducing fair value	9	9
Other assets
Derivative [Line Items]
Other assets	481	420
Other liabilities
Derivative [Line Items]
Other liabilities	388	333
Derivatives designated as hedging instruments:
Derivative [Line Items]
Notional amount	5,920	6,521
Derivatives designated as hedging instruments: | Other assets
Derivative [Line Items]
Other assets	89	78
Derivatives designated as hedging instruments: | Other liabilities
Derivative [Line Items]
Other liabilities	0	0
Derivatives designated as hedging instruments: | Interest rate swaps | Cash Flow Hedging
Derivative [Line Items]
Notional amount	850	1,450
Derivatives designated as hedging instruments: | Interest rate swaps | Fair Value Hedging
Derivative [Line Items]
Notional amount	0	0
Derivatives designated as hedging instruments: | Interest rate swaps | Other assets | Cash Flow Hedging
Derivative [Line Items]
Other assets	0	0
Derivatives designated as hedging instruments: | Interest rate swaps | Other assets | Fair Value Hedging
Derivative [Line Items]
Other assets	0	0
Derivatives designated as hedging instruments: | Interest rate swaps | Other liabilities | Cash Flow Hedging
Derivative [Line Items]
Other liabilities	0	0
Derivatives designated as hedging instruments: | Interest rate swaps | Other liabilities | Fair Value Hedging
Derivative [Line Items]
Other liabilities	0	0
Derivatives designated as hedging instruments: | Pay-fixed interest rate swaps | Cash Flow Hedging
Derivative [Line Items]
Notional amount	500	500	$ 500
Derivatives designated as hedging instruments: | Pay-fixed interest rate swaps | Other assets | Cash Flow Hedging
Derivative [Line Items]
Other assets	0	0
Derivatives designated as hedging instruments: | Pay-fixed interest rate swaps | Other liabilities | Cash Flow Hedging
Derivative [Line Items]
Other liabilities	0	0
Derivatives designated as hedging instruments: | Asset hedges: Pay-fixed interest rate swaps | Cash Flow Hedging
Derivative [Line Items]
Notional amount	1,000
Derivatives designated as hedging instruments: | Asset hedges: Pay-fixed interest rate swaps | Fair Value Hedging
Derivative [Line Items]
Notional amount	4,570	4,571
Derivatives designated as hedging instruments: | Asset hedges: Pay-fixed interest rate swaps | Other assets | Fair Value Hedging
Derivative [Line Items]
Other assets	89	78
Derivatives designated as hedging instruments: | Asset hedges: Pay-fixed interest rate swaps | Other liabilities | Fair Value Hedging
Derivative [Line Items]
Other liabilities	0	0
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	16,422	15,627
Derivatives not designated as hedging instruments | Other assets
Derivative [Line Items]
Other assets	392	342
Derivatives not designated as hedging instruments | Other liabilities
Derivative [Line Items]
Other liabilities	388	333
Derivatives not designated as hedging instruments | Customer-facing interest rate derivatives
Derivative [Line Items]
Notional amount	14,694	14,375
Derivatives not designated as hedging instruments | Customer-facing interest rate derivatives | Other assets
Derivative [Line Items]
Other assets	389	337
Derivatives not designated as hedging instruments | Customer-facing interest rate derivatives | Other liabilities
Derivative [Line Items]
Other liabilities	387	330
Derivatives not designated as hedging instruments | Other interest rate derivatives
Derivative [Line Items]
Notional amount	1,461	1,001
Derivatives not designated as hedging instruments | Other interest rate derivatives | Other assets
Derivative [Line Items]
Other assets	1	1
Derivatives not designated as hedging instruments | Other interest rate derivatives | Other liabilities
Derivative [Line Items]
Other liabilities	0	0
Derivatives not designated as hedging instruments | Foreign exchange derivatives
Derivative [Line Items]
Notional amount	267	216
Derivatives not designated as hedging instruments | Foreign exchange derivatives | Other assets
Derivative [Line Items]
Other assets	2	3
Derivatives not designated as hedging instruments | Foreign exchange derivatives | Other liabilities
Derivative [Line Items]
Other liabilities	1	3
Derivatives not designated as hedging instruments | Purchased credit derivatives
Derivative [Line Items]
Notional amount	0	35
Derivatives not designated as hedging instruments | Purchased credit derivatives | Other assets
Derivative [Line Items]
Other assets	0	1
Derivatives not designated as hedging instruments | Purchased credit derivatives | Other liabilities
Derivative [Line Items]
Other liabilities	$ 0	$ 0