Fair Value Measurements - Narrative (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value Measurements (Textual) [Abstract]
Impaired loans not covered under loss-share agreements	$ 27,265,000		$ 22,621,000
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Specific reserve included in allowance for loan losses	50,814,000		49,026,000
Impairment losses on mortgage servicing rights	3,132,000	$ 0	0
Changes in fair value, gain (loss)	3,895,000	$ 1,723,000
Impaired Loans, Not Covered
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Specific reserve included in allowance for loan losses	$ 1,847,000		$ 935,000