Investments - Equity Securities, FV-NI (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt and Equity Securities, FV-NI
Equity Securities, fair value	$ 98,588	$ 80,978
Equity securities, FV-NI Percent of Total	100.00%	100.00%
Mutual Fund
Debt and Equity Securities, FV-NI
Equity Securities, fair value	$ 58,942	$ 50,016
Equity securities, FV-NI Percent of Total	60.00%	60.00%
Public Utilities
Debt and Equity Securities, FV-NI
Equity Securities, fair value	$ 2,730	$ 1,759
Equity securities, FV-NI Percent of Total	0.00%	0.00%
Common Stock
Debt and Equity Securities, FV-NI
Equity Securities, fair value	$ 35,310	$ 27,198
Equity securities, FV-NI Percent of Total	40.00%	30.00%
Nonredeemable Preferred Stocks
Debt and Equity Securities, FV-NI
Equity Securities, fair value	$ 1,606	$ 2,005
Equity securities, FV-NI Percent of Total	0.00%	0.00%