Nonqualified Benefit Plans Investments (Details 6) - Supplemental Employee Retirement Plan - Unfunded Plan - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	$ 134,118	$ 121,930
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	87,009	73,838
Life insurance carried on plan participants
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	38,659	37,274
Other Investments
Defined Benefit Plan Disclosure [Line Items]
Investments in nonqualified benefit plans	$ 8,450	$ 10,818