Income Taxes - Significant Components of The Company's Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Deferred tax assets
Allowance for loan losses	$ 15,800	$ 13,966	$ 20,566
Loans	11,789	15,062	19,575
Deferred compensation	7,098	7,093	9,845
Securities	0	3,659	2,440
Net unrealized losses on securities - OCI	6,916	0	6,670
Impairment of assets	1,791	1,748	1,986
Federal and State net operating loss carryforwards	1,297	2,419	3,081
Intangibles	0	0	1,758
Other	4,310	4,722	3,577
Total deferred tax assets	49,001	48,669	69,498
Deferred tax liabilities
Investment in partnerships	548	757	1,272
Fixed assets	3,073	3,163	1,875
Mortgage servicing rights	11,224	10,139	3,360
Junior subordinated debt	2,352	2,394	4,004
Other	1,665	1,859	2,000
Total deferred tax liabilities	18,862	18,312	12,511
Net deferred tax assets	$ 30,139	$ 30,357	$ 56,987