Investments - Concentration of Credit Risk (Details)	Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract]
Insurance	15.00%
Electric utilities	11.00%
Banks	7.00%
Oil and natural gas pipelines	6.00%
Transportation	4.00%
Chemicals	4.00%
Oil and natural gas exploration and production	4.00%
Food	4.00%
Real estate investment trusts	4.00%
Telecommunications	3.00%