Description of Business and Summary of Significant Accounting Policies (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) depository_branch	Dec. 31, 2018 USD ($)	Jan. 01, 2019 USD ($)
Accounting Policies [Abstract]
Percentage of capital stock of the Bank held	100.00%
Number of depository branches | depository_branch	41
Cash and Cash Equivalents
Cash reserves required by the Board of Governors of the Federal Reserve for depository institutions (in dollars)	$ 0
Premises, furniture and equipment
Valuation allowance	0	$ 0
Reclassification of certain tax effects of the Tax Cuts and Jobs Act		0
Operating lease liabilities	46,498,000
Operating lease right of use assets	43,177,000
Accumulated Other Comprehensive Income (Loss)
Premises, furniture and equipment
Reclassification of certain tax effects of the Tax Cuts and Jobs Act		82,000
Accumulated Retained Earnings
Premises, furniture and equipment
Reclassification of certain tax effects of the Tax Cuts and Jobs Act		$ (82,000)
Accounting Standards Update 2016-02
Premises, furniture and equipment
Operating lease liabilities			$ 45,700,000
Operating lease right of use assets			43,800,000
Cumulative adjustment not recorded			$ 1,900,000
Minimum | Accounting Standards Update 2016-13
Premises, furniture and equipment
Allowance for credit losses	50,000,000
Maximum | Accounting Standards Update 2016-13
Premises, furniture and equipment
Allowance for credit losses	$ 60,000,000
Core Deposits | Minimum
Premises, furniture and equipment
Weighted average useful life (in years)	6 years
Core Deposits | Maximum
Premises, furniture and equipment
Weighted average useful life (in years)	11 years
Premises
Premises, furniture and equipment
Estimated useful life (in years)	40 years
Furniture, fixtures and equipment
Premises, furniture and equipment
Estimated useful life (in years)	7 years
Computer and telecommunication
Premises, furniture and equipment
Estimated useful life (in years)	3 years