Derivative Financial Instruments - Interest Rate Swaps Not Designated as Hedges (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Interest rate swap
Gains and losses on these derivative assets and liabilities recorded in non-interest expense in the unaudited Consolidated Statements of Income
Cash pledged to secure obligations	$ 25,600		$ 36,000
Interest rate swap | Not designated as hedging
Derivative Financial Instruments
Variable rate, commercial loans that are supported by the interest rate swap contracts	401,200		395,000
Notional Amount, Derivative Asset	401,247		394,954
Notional Amount, Derivative Liability	401,247		394,954
Fair values of derivative assets and liabilities recorded in consolidated balance sheets
Fair value recorded in other assets	22,090		32,685
Fair value recorded in other liabilities	22,090		32,685
Interest rate swaps - pay floating, receive fixed | Not designated as hedging
Derivative Financial Instruments
Notional Amount, Derivative Asset	308,178		394,954
Notional Amount, Derivative Liability	93,069
Fair values of derivative assets and liabilities recorded in consolidated balance sheets
Fair value recorded in other assets	18,881		32,685
Fair value recorded in other liabilities	3,209
Interest rate swaps - pay fixed, receive floating | Not designated as hedging
Derivative Financial Instruments
Notional Amount, Derivative Asset	93,069
Notional Amount, Derivative Liability	308,178		394,954
Fair values of derivative assets and liabilities recorded in consolidated balance sheets
Fair value recorded in other assets	3,209
Fair value recorded in other liabilities	18,881		$ 32,685
Non-interest expense | Interest rate swap
Gains and losses on these derivative assets and liabilities recorded in non-interest expense in the unaudited Consolidated Statements of Income
Gain (loss) pay, floating receive fixed	(10,595)	$ 23,478
Gain (loss) pay fixed receive floating	$ 10,595	$ (23,478)