Subordinated Debentures - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($)
Debt Instruments [Abstract]
Maximum number of consecutive quarters for deferral of interest payments on trust preferred securities	20
Size of company eligible for Tier 1 grandfather provision	$ 15,000,000,000
Number of years before allowed to prepay Tier 2 subordinated debt	5