Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Other Assets
Derivatives (included in Other Assets)
Fair value	$ 42,177	$ 78,319
Other Assets | Interest rate swap contracts—commercial loans
Derivatives (included in Other Assets)
Fair value	42,177	78,319
Notional amount	998,385	983,638
Collateral posted	0	0
Other Assets | Interest rate lock commitments—mortgage loans
Derivatives (included in Other Assets)
Fair value	812	2,900
Notional amount	22,674	51,053
Other Assets | Forward sale contracts—mortgage loans
Derivatives (included in Other Assets)
Fair value	101	0
Notional amount	18,915	0
Other Liabilities
Derivatives (included in Other Liabilities)
Fair value	42,554	79,033
Other Liabilities | Interest rate swap contracts—commercial loans
Derivatives (included in Other Liabilities)
Fair value	42,554	79,033
Notional amount	998,385	983,638
Collateral posted	43,190	77,930
Other Liabilities | Interest rate lock commitments—mortgage loans
Derivatives (included in Other Liabilities)
Fair value	0	0
Notional amount	0	0
Other Liabilities | Forward sale contracts—mortgage loans
Derivatives (included in Other Liabilities)
Fair value	0	385
Notional amount	$ 0	$ 47,062