Derivative Financial Instruments - Interest Rate Swaps Not Designated as Hedges (Details) - Interest rate swap - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Financial Instruments
Notional amount	$ 580,800	$ 243,700
Variable rate, commercial loans that are supported by the interest rate swap contracts	290,400	121,800
Gross gains and losses on derivative assets and liabilities recorded in Consolidated Statements of Income
Derivative cash pledged	18,100	1,000
Non-interest income
Gross gains and losses on derivative assets and liabilities recorded in Consolidated Statements of Income
Gross gains	10,915	1,176	$ 262
Non-interest expense
Gross gains and losses on derivative assets and liabilities recorded in Consolidated Statements of Income
Gross (losses)	(10,915)	(1,176)	$ (262)
Other assets
Fair values of derivative assets and liabilities recorded in consolidated balance sheets
Fair value recorded in other assets	12,354	1,438
Other liabilities
Fair values of derivative assets and liabilities recorded in consolidated balance sheets
Fair value recorded in other liabilities	$ 12,354	$ 1,438