Business Segments (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($) segment business_line branch
Business segments
Reportable segments | segment	4
Regional Bank
Business segments
Major business lines | business_line	7
Consumer and Business Banking Division | Regional Bank
Business segments
Number of full-service branches | branch	341
Small Business | Regional Bank
Business segments
Number of full-service branches | branch	341
Maximum | Small Business | Regional Bank
Business segments
Commercial banking customer revenues	$ 10
Maximum | Business Banking | Regional Bank
Business segments
Commercial banking customer revenues	50
Maximum | Commercial Banking | Regional Bank
Business segments
Commercial banking customer revenues	2,000
Minimum | Business Banking | Regional Bank
Business segments
Commercial banking customer revenues	10
Minimum | Commercial Banking | Regional Bank
Business segments
Commercial banking customer revenues	$ 50