Derivative Instruments and Hedging Activities - Balance Sheet Disclosures (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Interest rate swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	80,564,000	150,487,000
Interest rate swaps
Derivative [Line Items]
Notional Amount	300,000,000
Derivatives designated as hedging instruments:
Derivative [Line Items]
Notional Amount	1,200,000,000	1,100,000,000
Derivatives designated as hedging instruments: | Other Assets
Derivative [Line Items]
Other Assets	80,000	0
Derivatives designated as hedging instruments: | Other Liabilities
Derivative [Line Items]
Other Liabilities	349,000	179,000
Derivatives designated as hedging instruments: | Cash flow hedge interest rate swaps | Interest rate swaps
Derivative [Line Items]
Notional Amount	900,000,000	1,100,000,000
Derivatives designated as hedging instruments: | Cash flow hedge interest rate swaps | Interest rate swaps | Other Assets
Derivative [Line Items]
Other Assets	0	0
Derivatives designated as hedging instruments: | Cash flow hedge interest rate swaps | Interest rate swaps | Other Liabilities
Derivative [Line Items]
Other Liabilities	349,000	179,000
Derivatives designated as hedging instruments: | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Other Assets	80,000	0
Other Liabilities	0	0
Notional Amount	300,000,000	0
Derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional Amount	10,292,758,000	9,211,043,000
Derivatives not designated as hedging instruments: | Other Assets
Derivative [Line Items]
Other Assets	248,763,000	387,452,000
Derivatives not designated as hedging instruments: | Other Liabilities
Derivative [Line Items]
Other Liabilities	81,327,000	156,102,000
Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	9,962,230,000	8,889,557,000
Derivatives not designated as hedging instruments: | Interest rate swaps | Other Assets
Derivative [Line Items]
Other Assets	248,440,000	387,008,000
Derivatives not designated as hedging instruments: | Interest rate swaps | Other Liabilities
Derivative [Line Items]
Other Liabilities	80,215,000	154,025,000
Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Notional Amount	330,528,000	321,486,000
Derivatives not designated as hedging instruments: | Mortgage banking derivatives | Other Assets
Derivative [Line Items]
Other Assets	323,000	444,000
Derivatives not designated as hedging instruments: | Mortgage banking derivatives | Other Liabilities
Derivative [Line Items]
Other Liabilities	1,112,000	$ 2,077,000
Derivatives not designated as hedging instruments: | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Notional Amount	$ 10,400,000