Nature of Operations and Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) division operating_segment reporting_unit numberOfComponents quarter	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Number of bank divisions | division	16
Number of operating segments | operating_segment	1
Maximum period of original maturity to be included in cash and cash equivalents	three months
Federal reserve balance or cash on hand required	$ 0
Minimum period past due to consider loans as delinquent	30 days
Minimum period past due to consider loans as non accrual	90 days
Financing receivable, allowance for credit losses, forecasting period | quarter	4
Financing receivable, allowance for credit losses, number of components | numberOfComponents	2
Provision for credit losses on loan portfolio	$ 37,637,000	$ 57,000	$ 9,953,000
Provision for credit losses on off-balance sheet credit exposures	$ 2,128,000
Maximum term leases will be considered short-term	12 months
Maximum period up to which purchase price of business is allocated to assets acquired and liabilities assumed	1 year
Number of reporting units subsequent to aggregation for goodwill assessment | reporting_unit	1
Revenue from contracts with customers	$ 54,520,000	69,877,000	76,664,000
Impairment losses on receivables related to contracts with customers	$ 0	0
Percentage of likelihood for term more likely than not as it relates to income taxes	50.00%
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Adjustment to retained earnings due to adoption of amendments	$ (2,307,041,000)	(1,960,733,000)	(1,515,854,000)	$ (1,199,057,000)
Allowance for credit losses on loans	158,243,000	124,490,000	131,239,000	129,568,000
Deferred tax asset	0	2,037,000
Cumulative Effect, Period of Adoption, Adjustment
Adjustment to retained earnings due to adoption of amendments		12,347,000	25,114,000
Accounting Standards Update 2016-13
Allowance for credit losses on loans		3,720,000
ACL on off-balance sheet, credit exposures		12,817,000
Deferred tax asset		4,190,000
Retained Earnings
Adjustment to retained earnings due to adoption of amendments	$ (667,944,000)	(541,050,000)	(473,183,000)	$ (402,259,000)
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Adjustment to retained earnings due to adoption of amendments		$ 12,347,000	$ 25,114,000
Minimum Range
Period past due to consider loan as purchased credit-deteriorated loan	90 days
Minimum number of days delinquent to charge off loans	120 days
Number of years for home equity loan origination term	10
Period past due to consider loans as delinquent	30 days
Period past due to consider loans as non accrual	90 days
Minimum Range | Office Buildings
Useful life of premises and equipment	15 years
Minimum Range | Furniture, Fixtures and Equipment
Useful life of premises and equipment	3 years
Maximum Range
Number of years for home equity loan origination term	15 years
Period past due to consider loans as delinquent	89 days
Maximum Range | Office Buildings
Useful life of premises and equipment	40 years
Maximum Range | Furniture, Fixtures and Equipment
Useful life of premises and equipment	10 years