Shareholders' Equity - Comprehensive Capital Plan (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jul. 31, 2021
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends declared on Common Shares (in usd per share)	$ 0.185	$ 0.185	$ 0.370	$ 0.370
2021 Capital Plan
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock repurchased during period	$ 300,000,000
Cash dividends declared on Common Shares (in usd per share)	$ 0.185
2021 Capital Plan | Subsequent Event [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Stock repurchase program, amount authorized					$ 1,500,000,000
Open Market Share Repurchases
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock repurchased during period	$ 299,000,000
Employee Equity Compensation Programs
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common stock repurchased during period	$ 1,000,000