Derivative Financial Instruments - Fair Value Hedges (Details) - Interest rate swaps - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net gains and losses recognized in income related to derivatives in fair value hedging relationships
Net gains (losses) recognized on fair value hedges	$ (304,000)	$ (639,000)	$ (1,436,000)
Minimum | Fair value hedges
Fair hedges carried
Fixed interest rate (as a percent)	2.59%
Maximum | Fair value hedges
Fair hedges carried
Fixed interest rate (as a percent)	3.44%
Net interest income | Fair value hedges
Net gains and losses recognized in income related to derivatives in fair value hedging relationships
Expense recorded	$ (210,000)	(644,000)	(1,226,000)
Noninterest income
Net gains and losses recognized in income related to derivatives in fair value hedging relationships
Gains (losses) recognized on derivatives	629,000	846,000	956,000
Gains (losses) recognized on hedged item	(723,000)	(841,000)	(1,166,000)
Net gains (losses) recognized on fair value hedges (ineffective portion)	(94,000)	5,000	$ (210,000)
Derivatives designated as hedging instruments
Fair hedges carried
Notional amounts	41,317,000	194,687,000
Derivatives designated as hedging instruments | Fair value hedges
Fair hedges carried
Notional amounts	41,300,000	44,700,000
Positive fair value	0	0
Fair value losses	$ 0	$ 500,000