Fair Value - Changes in Fair Value Levels and in Level 3 Liabilities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair value
Asset transfers out of Level 1 into Level 2	$ 0	$ 0
Asset transfers into (out of) Level 3	0	0
Liability transfers out of Level 1 into Level 2	0	0
Liability transfers into (out of) Level 3	0	0
Visa derivative | Funding Swap (Visa Derivative)
Changes in Level 3 liabilities measured at fair value on a recurring basis
Balance	(2,607,000)	(5,439,000)
Total net losses included in other noninterest income	(5,354,000)	(173,000)
Settlements	3,728,000	3,005,000
Balance	(4,233,000)	(2,607,000)
Total net (losses) gains included in net income attributable to the change in unrealized gains or losses related to liabilities still held as of September 30,	$ (5,354,000)	$ (173,000)