Employee Benefits (Fair values of retirement plan assets) (Details 5) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined benefit pension plan disclosure
Fair value of plan assets	$ 93,638	$ 85,553	$ 96,908
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	93,638
Cash
Defined benefit pension plan disclosure
Fair value of plan assets	1,269	726
Cash | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	1,269
Large Cap [Member]
Defined benefit pension plan disclosure
Fair value of plan assets	1,731	1,593
Large Cap [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	1,731
Equity Security - Mutual Funds: Mixed-Cap
Defined benefit pension plan disclosure
Fair value of plan assets	29,336	25,298
Equity Security - Mutual Funds: Mixed-Cap | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	29,336
Equity Security - Mutual Funds: International
Defined benefit pension plan disclosure
Fair value of plan assets	23,961	21,621
Equity Security - Mutual Funds: International | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	23,961
Equity Security - Mutual Funds: Emerging Market
Defined benefit pension plan disclosure
Fair value of plan assets	2,342	2,150
Equity Security - Mutual Funds: Emerging Market | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	2,342
Fixed Income - Mutual Funds
Defined benefit pension plan disclosure
Fair value of plan assets	34,999	$ 34,165
Fixed Income - Mutual Funds | Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined benefit pension plan disclosure
Fair value of plan assets	$ 34,999