Investments - Equity Securities, FV-NI (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI
Equity Securities, FV-NI	$ 91,468	$ 80,978
Equity securities, FV-NI Percent of Total	100.00%	100.00%
Mutual Fund
Debt and Equity Securities, FV-NI
Equity Securities, FV-NI	$ 56,733	$ 50,016
Equity securities, FV-NI Percent of Total	60.00%	60.00%
Public Utilities [Member]
Debt and Equity Securities, FV-NI
Equity Securities, FV-NI	$ 2,260	$ 1,759
Equity securities, FV-NI Percent of Total	0.00%	0.00%
Common Stock
Debt and Equity Securities, FV-NI
Equity Securities, FV-NI	$ 30,794	$ 27,198
Equity securities, FV-NI Percent of Total	30.00%	30.00%
Nonredeemable Preferred Stocks
Debt and Equity Securities, FV-NI
Equity Securities, FV-NI	$ 1,681	$ 2,005
Equity securities, FV-NI Percent of Total	0.00%	0.00%