Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2020	Jan. 01, 2019	Sep. 01, 2018
Financing Receivable, Impaired [Line Items]
Date of discontinued recognition of interest on mortgage and commercial loans	90 days
Consumer and other retail loan due date	120 days
Minimum duration for past due residential loans to be considered as nonperforming	90 days
Impairment of company's goodwill	$ 0	$ 0	$ 0
Lock in period for interest rates	45 days
Right-of-use lease asset	$ 84,754,000
Lease liability	$ 88,494,000
Accounting Standards Update 2016-02
Financing Receivable, Impaired [Line Items]
Right-of-use lease asset					$ 53,042,000
Lease liability					$ 56,562,000
Minimum
Financing Receivable, Impaired [Line Items]
Renewal term	1 year
Minimum | Subsequent Event | Forecast | Accounting Standards Update 2016-13
Financing Receivable, Impaired [Line Items]
Allowance for credit loss				$ 35,000,000
Reserve for unfunded commitments				10,000,000
Maximum
Financing Receivable, Impaired [Line Items]
Renewal term	20 years
Maximum | Subsequent Event | Forecast | Accounting Standards Update 2016-13
Financing Receivable, Impaired [Line Items]
Allowance for credit loss				45,000,000
Reserve for unfunded commitments				$ 15,000,000
Premises
Financing Receivable, Impaired [Line Items]
Estimated life (in years)	40 years
Furniture and equipment | Minimum
Financing Receivable, Impaired [Line Items]
Estimated life (in years)	3 years
Furniture and equipment | Maximum
Financing Receivable, Impaired [Line Items]
Estimated life (in years)	7 years
Computer equipment | Minimum
Financing Receivable, Impaired [Line Items]
Estimated life (in years)	3 years
Computer equipment | Maximum
Financing Receivable, Impaired [Line Items]
Estimated life (in years)	5 years
Brand Group Holdings, Inc.
Financing Receivable, Impaired [Line Items]
Cash surrender value of life insurance						$ 40,081,000