Employee Benefits - Employee Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan Wage Base	$ 275,000	$ 270,000	$ 265,000
Deferred Compensation Arrangement with Individual, Requisite Service Period	3 years
Defined Contribution Plan, Cost	$ 1,800,000	1,500,000	$ 1,300,000
Deferred Compensation Arrangement with Individual, Compensation Expense	$ 100,000	$ 100,000
Base Percentage [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution percentage to retirement plan	13.20%
Excess Percentage for amounts above Social Security taxable wage base] [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution percentage to retirement plan	5.70%
Nonqualified Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contribution percentage to retirement plan	18.90%