Fair Value Measurements - Schedule of Change in Valuation of Securities (Detail) - USD ($) $ in Thousands |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | |||
Equity securities and warrants beginning balance | $ 2,768 | $ 2,768 | $ 2,768 |
Purchase of additional common stock | 500 | 0 | 0 |
Investment impairment charges | (4,678) | ||
Equity securities and warrants ending balance | 219 | 2,768 | 2,768 |
ASU 2016-01 [Member] | |||
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items] | |||
Impact of adoption of ASU 2016-01 recognized in other income | $ 1,629 | $ 0 | $ 0 |