Retirement Plans Employee Retirement Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Contribution Plan, Maximum Annual Contribution Per Employee, Percent	4.00%
Defined Contribution Plan, Employer Matching Contribution, Percent	100% of the first 3% and 50% of the next 2%
Defined Contribution Plan, Cost	$ 1,881	$ 1,630	$ 1,383
Supplemental Employee Retirement Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Year of Benefit	20 years