Financial Instruments and Fair Value Disclosures - Additional Information (Detail) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between fair value levels	$ 0		$ 0
Impairment charges	$ 71,268,000	$ 678,145,000
Measurement period for determining fair value of debt instruments	10 days
Level 1 [Member] | Cash Held in Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments	$ 242,200,000		125,700,000
Level 1 [Member] | Time Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of investments	$ 20,600,000		$ 20,600,000