Goodwill - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) reporting_unit	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Number of reporting units | reporting_unit			3
Recognized accumulated goodwill impairment losses	$ 7,507,104		$ 5,322,104		$ 4,852,104
Goodwill impairment	2,185,000	$ 0	$ 470,000	$ 0
Commercial Banking and Wealth
Acquired Finite-Lived Intangible Assets [Line Items]
Recognized accumulated goodwill impairment losses	3,200,000
Goodwill impairment	729,000
Retail Banking
Acquired Finite-Lived Intangible Assets [Line Items]
Recognized accumulated goodwill impairment losses	2,700,000
Goodwill impairment	1,300,000
Corporate and Investment Banking
Acquired Finite-Lived Intangible Assets [Line Items]
Recognized accumulated goodwill impairment losses	883,000
Goodwill impairment	164,000
Reporting units with no remaining goodwill balance
Acquired Finite-Lived Intangible Assets [Line Items]
Recognized accumulated goodwill impairment losses	$ 784,000