Liabilities - Accrued and other liabilities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accrued and other liabilities	$ 10,924	$ 6,103
Tax Related [Member]
Accrued and other liabilities	1,185	1,197
Accrued Compensation And Related Taxes [Member]
Accrued and other liabilities	2,924	3,424
Deferred revenue [Member]
Accrued and other liabilities	3,570	299
Insurance [Member]
Accrued and other liabilities	1,483	0
Professional services [Member]
Accrued and other liabilities	251	282
Accrued fuel and rig-related charges [Member]
Accrued and other liabilities	810	162
Other accrued expenses [Member]
Accrued and other liabilities	$ 701	$ 739