Recent Accounting and Regulatory Pronouncements - Narrative (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impairment of goodwill		$ 0
Impairment of other intangible		0
Additional allowance for credit losses for loans		440,159	$ 434,608			$ 56,927	$ 60,255	$ 58,213	$ 55,798
Deferred tax assets		107,500				31,316	27,844
Additional reserve for unfunded commitments		43,200
Retained earnings		$ 604,564				679,895	$ 646,325
ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Additional allowance for credit losses for loans	[1]			$ 54,438
Deferred tax assets	[2]			12,639
Additional reserve for unfunded commitments				6,400
Retained earnings				$ (44,820)	[3]	$ 44,800

[1] This is the calculated adjustment to the ACL related to the adoption of ASC 326. Additional reserve related to non-acquired loans was $34,049, to acquired loans was $16,981 and to purchased credit deteriorated loans was $3,408.

[2] This is the effect of deferred tax assets related to the adjustment to the ACL from the adoption of ASC 326 using a 22% tax rate.

[3] This is the net adjustment to retained earnings related to the adoption of ASC 326.