Accumulated Other Comprehensive (Loss) Income - Schedule of Changes in Components of AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	$ 19,216.0	$ 10,570.0	$ 9,662.0	$ 4,738.0
AOCI activity before reclassifications			(50.0)	(481.0)
Amounts reclassified from AOCI to earnings			13.0	6.0
Other comprehensive (loss) income for the period	(103.0)	(160.0)	(37.0)	(475.0)
Ending balance, shareholders' equity	19,771.0	10,642.0	19,771.0	10,642.0
Total accumulated other comprehensive (loss) income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	(669.0)	(305.0)	(735.0)	10.0
Other comprehensive (loss) income for the period	(103.0)	(160.0)	(37.0)	(475.0)
Ending balance, shareholders' equity	(772.0)	(465.0)	(772.0)	(465.0)
Unrealized loss on securities available for sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity			(739.0)	(9.0)
AOCI activity before reclassifications			(54.0)	(481.0)
Amounts reclassified from AOCI to earnings			12.0	0.0
Other comprehensive (loss) income for the period			(42.0)	(481.0)
Ending balance, shareholders' equity	(781.0)	(490.0)	(781.0)	(490.0)
Unrealized loss on securities available for sale transferred to held to maturity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity			(6.0)	(7.0)
AOCI activity before reclassifications	0.0	0.0	0.0	0.0
Amounts reclassified from AOCI to earnings			1.0	1.0
Other comprehensive (loss) income for the period	1.0	0.0	1.0	1.0
Ending balance, shareholders' equity	(5.0)	(6.0)	(5.0)	(6.0)
Defined benefit pension items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity			10.0	26.0
AOCI activity before reclassifications	(4.0)	0.0	4.0	0.0
Amounts reclassified from AOCI to earnings			0.0	5.0
Other comprehensive (loss) income for the period	(4.0)	3.0	4.0	5.0
Ending balance, shareholders' equity	$ 14.0	$ 31.0	$ 14.0	$ 31.0