Investments (Reverse Purchase Agreements) (Details) - USD ($) $ in Millions |
Mar. 31, 2019 |
Dec. 31, 2018 |
---|---|---|
Investments, Debt and Equity Securities [Abstract] | ||
Value of reverse repurchase agreements | $ 99.9 | $ 3.7 |
Minimum required collateral for reverse repurchase agreements, expressed as a percentage of loan principal | 102.00% |