Nature of Operations and Summary of Significant Accounting Policies (Details)	9 Months Ended
	Sep. 30, 2020 USD ($) numberOfComponents operating_segment quarter division	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of bank divisions | division	16
Number of operating segments | operating_segment	1
Forecasting period used to determine ACL | quarter	4
Number of components used in methodology in determining ACL | numberOfComponents	2
Maximum term leases will be considered short-term	12 months
Revenue from contracts with customers	$ 40,184,000	$ 54,608,000
Impairment losses on receivables related to contracts with customers	0			$ 0
Adjustment to retained earnings due to adoption of amendments	(2,255,089,000)	(1,953,401,000)	$ (2,203,715,000)	(1,960,733,000)	$ (1,687,376,000)	$ (1,515,854,000)
Allowance for credit losses on loans	164,552,000	125,535,000	162,509,000	124,490,000	129,054,000	131,239,000
Deferred tax asset	$ 0			2,037,000
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Retained Earnings Substantially Restricted
Adjustment to retained earnings due to adoption of amendments	$ (629,109,000)	$ (528,599,000)	$ (580,035,000)	(541,050,000)	$ (503,773,000)	$ (473,183,000)
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
Accounting Standards Update 2016-13 | Retained Earnings Substantially Restricted
Adjustment to retained earnings due to adoption of amendments				$ 12,347,000
Minimum
Period past due to consider loan as delinquent	30 days
Period past due to consider loan as non accrual	90 days
Period past due to consider loan as purchased credit-deteriorated loan	90 days
Number of days delinquent to charge off loans	120 days
Number of years for home equity loan origination term	10 years
Maximum
Period past due to consider loan as delinquent	89 days
Number of years for home equity loan origination term	15 years