Income Taxes - Significant Components of The Company's Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Deferred tax assets
Allowance for loan losses	$ 14,030	$ 13,966	$ 20,421
Loans	20,044	15,062	25,585
Deferred compensation	9,441	7,093	10,857
Securities	0	3,659	2,573
Net unrealized losses on securities - OCI	8,340	0	1,942
Impairment of assets	1,774	1,748	2,383
Federal and State net operating loss carryforwards	21,478	2,419	3,338
Intangibles	0	0	0
Other	5,729	4,722	7,319
Total deferred tax assets	80,836	48,669	74,418
Deferred tax liabilities
Investment in partnerships	1,673	757	946
Intangibles	0	0	428
Fixed assets	3,645	3,163	1,429
Mortgage servicing rights	11,224	10,139	3,360
Junior subordinated debt	1,562	2,394	3,620
Other	1,747	1,859	1,770
Total deferred tax liabilities	19,851	18,312	11,553
Net deferred tax assets	$ 60,985	$ 30,357	$ 62,865