Equity Method Investments - Equity in Earnings (Loss) of Joint Ventures (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Equity In earnings (loss)	$ 1,776	$ 664	$ 1,079	$ 517	$ 92	$ 1,562	$ 3,096	$ 1,352	$ 4,036	$ 6,102	$ 10,137
ICP (30% interest) [Member]
Schedule of Equity Method Investments [Line Items]
Equity In earnings (loss)									4,069	6,242	10,098
DMI (50% interest) [Member]
Schedule of Equity Method Investments [Line Items]
Equity In earnings (loss)									$ (33)	$ (140)	$ 39