Loans - Summary of Allowance for Loan Losses by Portfolio Class and Category (Details) - USD ($) $ in Thousands	3 Months Ended
Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018			$ 43,476
Balance	$ 44,555
Portfolio loans, net
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	42,935	$ 41,945	42,295
Provision (provision reversal) for loan losses	1,833	1,960	1,476
Losses charged off	(1,658)	(1,890)	(2,250)
Recoveries	588	920	424
Balance	43,698	42,935	41,945
Portfolio loans, net \| Commercial and industrial
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	29,093	28,660	29,039
Provision (provision reversal) for loan losses	867	1,781	1,445
Losses charged off	(1,295)	(1,380)	(1,853)
Recoveries	209	32	29
Balance	28,874	29,093	28,660
Portfolio loans, net \| CRE - investor owned
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	5,324	5,339	4,683
Provision (provision reversal) for loan losses	333	364	769
Losses charged off	0	(431)	(120)
Recoveries	11	52	7
Balance	5,668	5,324	5,339
Portfolio loans, net \| CRE - owner occupied
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	4,371	3,774	4,239
Provision (provision reversal) for loan losses	419	591	(431)
Losses charged off	(22)	0	(36)
Recoveries	3	6	2
Balance	4,771	4,371	3,774
Portfolio loans, net \| Construction and land development
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	1,972	1,699	1,987
Provision (provision reversal) for loan losses	(88)	(216)	(252)
Losses charged off	0	0	(45)
Recoveries	260	489	9
Balance	2,144	1,972	1,699
Portfolio loans, net \| Residential real estate
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	1,378	1,625	1,616
Provision (provision reversal) for loan losses	193	(345)	(288)
Losses charged off	(255)	(26)	(67)
Recoveries	65	124	364
Balance	1,381	1,378	1,625
Portfolio loans, net \| Consumer and other
Allowance for Loan Losses [Roll Forward]
Balance at December 31, 2018	797	848	731
Provision (provision reversal) for loan losses	109	(215)	233
Losses charged off	(86)	(53)	(129)
Recoveries	40	217	13
Balance	$ 860	$ 797	$ 848

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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