Employee Benefit Plans - Retrospective Application of the Statement of Income (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Compensation and employee benefits	$ 15,624	$ 84,256	$ 77,226	$ 62,993
Other non-interest expense	$ 3,780	$ 11,769	5,597	$ 14,207
Accounting Standards Update 2017-07
Defined Benefit Plan Disclosure [Line Items]
Compensation and employee benefits			77,226
Other non-interest expense			5,597
Accounting Standards Update 2017-07 | Previously Reported
Defined Benefit Plan Disclosure [Line Items]
Compensation and employee benefits			69,907
Other non-interest expense			$ 12,916