Shareholders' Equity - Comprehensive Capital Plan (Details) - USD ($)	3 Months Ended				12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends declared per common share (in dollars per share)					$ 0.71	$ 0.565	$ 0.38
2019 Capital Plan [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Authorized amount of share repurchases	$ 1,000,000,000.0				$ 1,000,000,000.0
Common shares repurchased, value					489,000,000
Cash dividends declared per common share (in dollars per share)	$ 0.185	$ 0.185
2018 Capital Plan [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common shares repurchased, value					$ 379,000,000
Cash dividends declared per common share (in dollars per share)			$ 0.17	$ 0.17