Fair Value Measurements - Fair Value of Certain Investments Based on NAV (Parenthetical) (Detail) - USD ($) $ in Thousands |
Jun. 30, 2018 |
Dec. 31, 2017 |
---|---|---|
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items] | ||
Unfunded Commitments | $ 8,650 | $ 10,300 |
Private Equity Funds [Member] | Consolidated But Not Owned [Member] | ||
Fair Value Investments Entities That Calculate Net Asset Value Per Share [Line Items] | ||
Unfunded Commitments | $ 15,517 | $ 5,902 |