Schedule of Vessel Commitments (Parenthetical) (Detail) $ in Thousands	1 Months Ended	9 Months Ended
	Jan. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) Vessel	Sep. 30, 2015 USD ($)
Significant Purchase and Supply Commitment [Line Items]
Refunds from cancelled vessel construction contracts		$ 43,000	$ 31,000
Refunds from cancelled vessel construction contracts		$ 36,190
Option Agreement
Significant Purchase and Supply Commitment [Line Items]
Number of vessels under construction | Vessel		6
Subsequent Event
Significant Purchase and Supply Commitment [Line Items]
Refunds from cancelled vessel construction contracts	$ 12,000