Derivative Instruments and Hedging Activities - Balance Sheet Disclosures (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Interest rate swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	17,956	150,487
Derivatives designated as hedging instruments:
Derivative [Line Items]
Notional Amount	1,100,000	1,100,000
Derivatives designated as hedging instruments: | Other Assets
Derivative [Line Items]
Other Assets	0	0
Derivatives designated as hedging instruments: | Other Liabilities
Derivative [Line Items]
Other Liabilities	88	179
Derivatives designated as hedging instruments: | Cash flow hedge interest rate swaps | Interest rate swaps
Derivative [Line Items]
Notional Amount	1,100,000	1,100,000
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	88	179
Derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional Amount	9,822,126	9,211,043
Derivatives not designated as hedging instruments: | Other Assets
Derivative [Line Items]
Other Assets	155,633	387,452
Derivatives not designated as hedging instruments: | Other Liabilities
Derivative [Line Items]
Other Liabilities	22,415	156,102
Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	9,375,183	8,889,557
Derivatives not designated as hedging instruments: | Interest rate swaps | Other Assets
Derivative [Line Items]
Other Assets	153,859	387,008
Derivatives not designated as hedging instruments: | Interest rate swaps | Other Liabilities
Derivative [Line Items]
Other Liabilities	17,956	154,025
Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Notional Amount	446,943	321,486
Derivatives not designated as hedging instruments: | Mortgage banking derivatives | Other Assets
Derivative [Line Items]
Other Assets	1,774	444
Derivatives not designated as hedging instruments: | Mortgage banking derivatives | Other Liabilities
Derivative [Line Items]
Other Liabilities	$ 4,459	$ 2,077