Fair Value Measurements - Components of Long-Term Debt and Methods Used in Estimating Fair Values (Parenthetical) (Detail)	Jun. 30, 2020
4.25% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.25%
3.90% Promissory Note [Member]
Debt Instrument [Line Items]
Debt instrument stated interest rate	3.90%
4% Promissory Note [Member]
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.00%
3.75% Callable Promissory Note [Member]
Debt Instrument [Line Items]
Debt instrument stated interest rate	3.75%
4.55% Promissory Note [Member]
Debt Instrument [Line Items]
Debt instrument stated interest rate	4.55%