Employee Benefits - Asset Held in Rabbi Trust by Plan Type (Details) - Primary Beneficiary - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Book Value	$ 78,122	$ 71,833
Mark-to-Market	20,052	19,850
Fair Value	98,174	91,683
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Book Value	4,476	5,157
Fair Value	4,476	5,157
Equities
Defined Benefit Plan Disclosure [Line Items]
Book Value	65,670	59,235
Mark-to-Market	19,880	19,492
Fair Value	85,550	78,727
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Book Value	7,976	7,441
Mark-to-Market	172	358
Fair Value	$ 8,148	$ 7,799