Derivative Instruments and Hedging Activities - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) swap	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) swap	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Derivative [Line Items]
Number of credit swaps | swap	23		23
Aggregate fair value of net liability position	$ 184,100,000		$ 184,100,000
Interest rate swaps
Derivative [Line Items]
Accumulated net after-tax losses related to effective cash flow hedges	4,700,000		4,700,000		$ 3,700,000
Estimated amount of interest rate derivatives to be reclassified to interest expense			3,800,000
Fair value hedge | Noninterest Income | Interest rate swaps
Derivative [Line Items]
Fee income related to derivative interest rate swaps executed with commercial loan customers	19,200,000	$ 13,900,000	48,100,000	$ 23,400,000
Derivatives designated as hedging instruments
Derivative [Line Items]
Notional amount	1,182,079,000		1,182,079,000		187,281,000
Derivatives designated as hedging instruments | Cash flow hedge
Derivative [Line Items]
Notional amount	1,100,000,000		1,100,000,000
Derivatives designated as hedging instruments | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Notional amount	7,079,000		7,079,000		7,281,000
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	8,827,975,000		8,827,975,000		4,255,866,000
Aggregate notional amount of derivative asset	181,500,000		181,500,000
Derivatives not designated as hedging instruments | Interest rate swaps
Derivative [Line Items]
Notional amount	$ 8,306,557,000		$ 8,306,557,000		$ 4,113,106,000
Derivatives not designated as hedging instruments | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Number of instruments held | swap	2		2
Derivatives not designated as hedging instruments | Fair value hedge | Steepener swap, derivative one
Derivative [Line Items]
Notional amount	$ 10,400,000		$ 10,400,000
Derivatives not designated as hedging instruments | Fair value hedge | Steepener swap, derivative two
Derivative [Line Items]
Notional amount	$ 10,400,000		$ 10,400,000
Minimum | Derivatives designated as hedging instruments | Cash flow hedge
Derivative [Line Items]
Fixed interest rate	0.05%		0.05%
Maximum | Derivatives designated as hedging instruments | Cash flow hedge
Derivative [Line Items]
Fixed interest rate	0.67%		0.67%