Financial Instruments and Fair Value Disclosures - Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impairment of assets	$ 774,028
Nonrecurring Fair Value Measurements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired assets	175,400
Impairment of assets	774,028
Money Market Funds [Member] | Fair Value Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	482,699	$ 135,300
Level 1 [Member] | Money Market Funds [Member] | Fair Value Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total short-term investments	482,699	$ 135,300
Level 3 [Member] | Nonrecurring Fair Value Measurements [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Impaired assets	$ 175,400