Allowance for Credit Losses - Aggregated analysis of the changes in allowance for loan losses Summary (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Allowance for credit losses
Balance at beginning of period	$ 56,927	$ 55,798
Loans charged-off	(3,223)	(1,619)
Recoveries of loans previously charged off	1,909	958
Net charge-offs	(1,314)	(661)
Provision for loan losses charged to operations	34,734	1,488
Reduction due to loan removals		(103)
Balance at end of period	$ 144,785	56,522
Non-acquired loans
Allowance for credit losses
Balance at beginning of period		51,194
Loans charged-off		(1,245)
Recoveries of loans previously charged off		752
Net charge-offs		(493)
Provision for loan losses charged to operations		1,307
Balance at end of period		52,008
Acquired non-credit impaired loans
Allowance for credit losses
Loans charged-off		(374)
Recoveries of loans previously charged off		206
Net charge-offs		(168)
Provision for loan losses charged to operations		168
Acquired credit impaired loans
Allowance for credit losses
Balance at beginning of period		4,604
Provision for loan losses charged to operations		13
Reduction due to loan removals		(103)
Balance at end of period		$ 4,514