Employee Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) hour	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Percentage of employer contribution fully vested	100.00%
Carrying value of obligation related to deferred compensation plan	$ 3,700,000	$ 2,800,000
Salary Continuation Plan expense	184,000	0	$ 0
Accrued expenses and other liabilities
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Salary Continuation Plan	4,600,000
Accrued expenses and other liabilities | Washington Banking
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Carrying value of obligation	$ 268,000	250,000
401(k) Plan and Trust Salary Saving Plan
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Minimum service days required for eligibility under the plan	30 days
Employer matching contribution, percent of employee's gross pay	50.00%
Maximum annual contributions per employee, percent	3.00%
Defined contribution plan, employer matching contribution amount	$ 1,400,000	1,100,000	1,000,000
401(k) Plan and Trust
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Minimum hours of service required for eligibility under the plan | hour	1,000
Minimum age required for eligibility under the plan	18 years
Employer profit sharing contributions	$ 0	0	0
Deferred Compensation Plan
Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items]
Compensation expense	810,000	652,000	540,000
Company's contributions	$ 583,000	$ 453,000	$ 521,000