Other Real Estate Owned and Repossessed Assets - Rollforward Tables (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Repossessed Assets [Line Items]
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]				$ 1,339
Changes in other real estate owned
Balance at the beginning of the period		$ 5,832	$ 8,182
Transfers			(189)
Other additions		4,137	1,638
Net payments received		(164)	(103)
Disposals		(852)	(1,678)
Write-downs		(294)	(651)
Balance at the end of the period		8,659	7,199
Changes in repossessed assets
Balance at the beginning of the period		424	625
Transfers			0
Other additions		740	846
Net payments received		0	0
Disposals		(717)	(951)
Write-downs		0	0
Balance at the end of the period		447	$ 520
Retained earnings
Repossessed Assets [Line Items]
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]				$ 1,680
ASU 2014-09
Repossessed Assets [Line Items]
Loans to facilitate reclassified to loans		$ 1,100
ASU 2014-09 | Retained earnings
Repossessed Assets [Line Items]
Cumulative effect adjustment of change in accounting policy, net of tax impact				$ 900

[1] Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 6, Other Real Estate Owned and Repossessed Assets and Note 20, Accumulated Other Comprehensive Loss for further details on changes in accounting policy.