Loans Receivable - Purchased Credit Impaired Loans (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Impaired [Line Items]
Outstanding Principal	$ 28,461	$ 46,639
Recorded Investment	24,907	40,603
Commercial business
Financing Receivable, Impaired [Line Items]
Outstanding Principal	22,834	35,343
Recorded Investment	17,707	27,769
Commercial business | Commercial and industrial
Financing Receivable, Impaired [Line Items]
Outstanding Principal	6,319	8,818
Recorded Investment	3,433	2,912
Commercial business | Owner-occupied commercial real estate
Financing Receivable, Impaired [Line Items]
Outstanding Principal	7,830	12,230
Recorded Investment	7,215	11,515
Commercial business | Non-owner occupied commercial real estate
Financing Receivable, Impaired [Line Items]
Outstanding Principal	8,685	14,295
Recorded Investment	7,059	13,342
One-to-four family residential
Financing Receivable, Impaired [Line Items]
Outstanding Principal	3,169	4,120
Recorded Investment	3,315	5,255
Real estate construction and land development
Financing Receivable, Impaired [Line Items]
Outstanding Principal	255	3,202
Recorded Investment	423	2,124
Real estate construction and land development | One-to-four family residential
Financing Receivable, Impaired [Line Items]
Outstanding Principal	67	841
Recorded Investment	380	89
Real estate construction and land development | Five or more family residential and commercial properties
Financing Receivable, Impaired [Line Items]
Outstanding Principal	188	2,361
Recorded Investment	43	2,035
Consumer
Financing Receivable, Impaired [Line Items]
Outstanding Principal	2,203	3,974
Recorded Investment	$ 3,462	$ 5,455