Summary of Book Value and Fair Value of Current and Long Term Portion of Loans Payable (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Fair Value, Measurement Inputs, Disclosure
Current portion of loans payable, Book Value	$ 70,672		$ 91,597
Long-term portion of loans payable, Book Value	33,381		32,133
Total loans payable, Book Value	104,053
Current portion of loans payable, Fair Value	70,672	[1]
Long-term portion of loans payable, Fair Value	33,381	[1]
Total loans payable, Fair Value	$ 104,053	[1]

[1] Estimated fair value of long-term debt is measured using the income approach. This fair value measurement is based on similar grade US Treasury security re-priced at June 30, 2012 plus contractual spread and thus represents Level 2 inputs under the fair value hierarchy.