Derivative Financial Instruments and Hedging - Gross notional and fair value amounts of derivatives (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Notional values	$ 612,181	$ 292,860
Asset derivatives	7,490	3,504
Liability derivatives	3,758	876
Interest Risk, Interest Rate Lock Commitments
Derivative [Line Items]
Notional values	279,048	122,477
Asset derivatives	7,336	3,460
Liability derivatives	0	0
Interest Risk, Forward Delivery Contracts
Derivative [Line Items]
Notional values	87,773	41,383
Asset derivatives	36	5
Liability derivatives	0	52
Interest Risk, TBA Mortgage Backed Securities
Derivative [Line Items]
Notional values	235,000	129,000
Asset derivatives	118	39
Liability derivatives	428	824
Other Contract
Derivative [Line Items]
Notional values	10,360	0
Asset derivatives	0	0
Liability derivatives	$ 3,330	$ 0