Fair Value, Carrying Value and Fair Value by Level of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets [Abstract]
Limited partnerships	$ 7,214	$ 23,292
Carrying Value [Member]
Assets [Abstract]
Limited partnerships	7,214	23,292
Commercial mortgage loans	10,602	11,782
Liabilities [Abstract]
Short-term borrowings	20,000	20,000
Fair Value [Member]
Assets [Abstract]
Limited partnerships	7,214	23,292
Commercial mortgage loans	11,425	12,068
Liabilities [Abstract]
Short-term borrowings	20,000	20,000
Fair Value [Member] | Level 1 [Member]
Assets [Abstract]
Limited partnerships	0	0
Commercial mortgage loans	0	0
Liabilities [Abstract]
Short-term borrowings	0	0
Fair Value [Member] | Level 2 [Member]
Assets [Abstract]
Limited partnerships	0	0
Commercial mortgage loans	0	0
Liabilities [Abstract]
Short-term borrowings	20,000	20,000
Fair Value [Member] | Level 3 [Member]
Assets [Abstract]
Limited partnerships	7,214	23,292
Commercial mortgage loans	11,425	12,068
Liabilities [Abstract]
Short-term borrowings	$ 0	$ 0