Derivative Investments (Balance Sheet) (Details) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Derivatives, Fair Value [Line Items] | ||
| Derivatives, index options | $ 120,644 | $ 38,409 |
| Liability Derivatives | 122,666 | 58,359 |
| Not Designated as Hedging Instrument | ||
| Derivatives, Fair Value [Line Items] | ||
| Derivatives, index options | 120,644 | 38,409 |
| Liability Derivatives | 122,666 | 58,359 |
| Not Designated as Hedging Instrument | Equity index options | Derivatives, index options | ||
| Derivatives, Fair Value [Line Items] | ||
| Derivatives, index options | 120,644 | 38,409 |
| Not Designated as Hedging Instrument | Fixed-index products | Universal Life and Annuity Contracts | ||
| Derivatives, Fair Value [Line Items] | ||
| Liability Derivatives | $ 122,666 | $ 58,359 |