Financial Instruments and Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on Recurring and Nonrecurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets:
Loss on assets	$ 678,100	$ 499,400	$ 2,600	$ 358,500	$ 678,145	$ 860,441	$ 109,462
Carrying value of impaired assets		175,400			45,100	175,400
Fair Value Measurements, Recurring [Member]
Assets:
Short-term investments		105,659			146,360	105,659
Mortgage-backed securities		80			35	80
Total assets		117,177			146,395	117,177
Corporate bonds		11,438				11,438
Fair Value Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Short-term investments		105,659			146,360	105,659
Total assets		105,659			146,360	105,659
Fair Value Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Mortgage-backed securities		80			35	80
Total assets		11,518			35	11,518
Corporate bonds		11,438				11,438
Nonrecurring Fair Value Measurements [Member]
Assets:
Loss on assets					678,145	860,441
Carrying value of impaired assets		189,600			69,153	189,600
Nonrecurring Fair Value Measurements [Member] | Level 3 [Member]
Assets:
Carrying value of impaired assets		$ 189,600			$ 69,153	$ 189,600