Fair Value Measurements - Measured Under Certain Conditions (Details) - USD ($) |
9 Months Ended | |
---|---|---|
Sep. 30, 2019 |
Sep. 30, 2018 |
|
Financing Receivable, Impaired [Line Items] | ||
Realized investment losses on assets measured at fair value under certain conditions, after-tax | $ 0 | |
Realized investment gains on equity securities with no readily determinable fair value | $ 0 | |
Maximum [Member] | ||
Financing Receivable, Impaired [Line Items] | ||
Assets measured at fair value under certain conditions as a percent of total investments | 1.00% | 1.00% |