Summary Of Significant Accounting Policies (Details) $ in Millions		12 Months Ended
	Dec. 31, 2017 USD ($) States	Dec. 31, 2017 USD ($) States	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of States in which Entity Operates | States	11	11
Security resell agreements maturity days	30
Customer Securities for which Entity has Right to Sell or Repledge, Fair Value	$ 287	$ 287
Security resell agreements maximum amount, outstanding	$ 1,800	$ 1,800
Percentage of acquired assets and all assumed liabilities recognized in business combination	100.00%
Estimated useful lives of core deposit assets and other intangibles (in years)	12 years
Number of variable interest entities consolidated	0	0	0
Security resell agreements average amount		$ 360
Minimum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of properties, Minimum (in years)	25 years
Minimum [Member] | Furniture And Equipment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of properties, Minimum (in years)	3 years
Minimum [Member] | Software License Arrangement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of properties, Minimum (in years)	3 years
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of properties, Minimum (in years)	40 years
Maximum [Member] | Furniture And Equipment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of properties, Minimum (in years)	10 years
Maximum [Member] | Software License Arrangement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated useful lives of properties, Minimum (in years)	10 years