Allowance for Credit Losses - Aggregated analysis of the changes in allowance for loan losses Summary (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Allowance for credit losses
Balance at beginning of period	$ 144,785	$ 56,522	$ 56,927	$ 55,798
Loans charged-off	(2,431)	(2,862)	(5,654)	(4,481)
Recoveries of loans previously charged off	2,330	991	4,239	1,949
Net charge-offs	(101)	(1,871)	(1,415)	(2,532)
Provision for loan losses charged to operations	29,536	3,704	64,270	5,192
Reduction due to loan removals		(142)		(245)
Balance at end of period	$ 434,608	58,213	$ 434,608	58,213
Non-acquired loans
Allowance for credit losses
Balance at beginning of period		52,008		51,194
Loans charged-off		(1,327)		(2,572)
Recoveries of loans previously charged off		875		1,627
Net charge-offs		(452)		(945)
Provision for loan losses charged to operations		2,034		3,341
Balance at end of period		53,590		53,590
Acquired non-credit impaired loans
Allowance for credit losses
Loans charged-off		(1,535)		(1,909)
Recoveries of loans previously charged off		116		322
Net charge-offs		(1,419)		(1,587)
Provision for loan losses charged to operations		1,419		1,587
Acquired credit impaired loans
Allowance for credit losses
Balance at beginning of period		4,514		4,604
Provision for loan losses charged to operations		251		264
Reduction due to loan removals		(142)		(245)
Balance at end of period		$ 4,623		$ 4,623