Derivative Financial Instruments - Carrying Amount and Adjustment (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amortized cost, at fair value	$ 547,034	$ 499,893
Derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amortized cost, at fair value	88,200
Loans | Derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying amount of the hedged assets	485,097	474,233
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	27,643	4,961
Securities available-for-sale | Derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying amount of the hedged assets	155,850	159,188
Cumulative amount of fair value hedging adjustment included in the carrying amount of the hedged assets	$ 3,727	$ (229)