Income Taxes And Tax-Related Items Income Taxes And Tax-Related Items (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Liability, net unrealized gains on investment securities available-for-sale	$ (20)				$ 0				$ (20)	$ 0
Deferred Tax Liability, Hedging gains and losses	(10)				0				(10)	0
Deferred Tax Assets, Operating Lease Liability	77				0				77	0
Income before income taxes									1,532	1,535	$ 1,234
Foreign-source income									42
Reductionindeferredtaxadjustment										99
Remeasurement of the Corporation's deferred tax balance									0	8	(107)
Tax benefits from employee stock transactions recorded in income statement									(12)	(23)	(35)
Provision for income taxes	82	$ 80	$ 87	$ 85	90	$ 63	$ 54	$ 93	334	300	$ 491
Liability for tax-related interest and penalties	8				7				8	7
Reasonably possible change in unrecognized tax benefits in next 12 months	5								5
Unrecognized tax benefits that would impact the effective tax rate	14				11				14	11
State net operating loss carryforwards	3				4				3	4
Deferred tax asset valuation allowance	$ 3				$ 3				$ 3	$ 3
Minimum
Years state net operating loss carryforwards expire									Dec. 31, 2019
Maximum
Years state net operating loss carryforwards expire									Dec. 31, 2028