Investments - Schedule Of Fair Value Measurement Inputs and Valuation Techniques (Detail)	Dec. 31, 2019
Risk free rate | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	2.46
Risk free rate | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	1.58
Equity Volatility | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	106
Equity Volatility | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	58
Market Yield | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	18
Market Yield | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	15
Probability of Qualified Financing
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	0
Probability of Sale
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	30
Probability of No Event
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Alternative investment, measurement input	70