Summary of Long-Term Debt Obligations (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Long-term debt consists of:
Long-term borrowing	$ 102,708	$ 93,735
Less: Amounts due within one year	14,146	8,941
Total long-term debt	88,562	84,794
North Ocean Construction Financing | North Ocean 102
Long-term debt consists of:
Long-term borrowing	37,349	43,325
North Ocean Construction Financing | North Ocean 105
Long-term debt consists of:
Long-term borrowing	$ 65,359	$ 50,410