Loans Payable - Additional Information (Detail) (USD $)	1 Months Ended
	Feb. 28, 2011 Year	Aug. 31, 2009 Year	Jun. 30, 2012	Dec. 31, 2011
Line of Credit Facility
Revolving credit facility, term (years)	5
Revolving credit facility, maximum borrowing capacity	$ 100,000,000
Applicable margin on LIBOR	2.75%
Credit Agreement potential floating interest rate plus Federal Funds Rate	0.50%
Margin increase on Wells Fargo's prime rate			1.50%
Revolving credit facility, fees	500,000
Letter of credit			5,000,000
Revolving credit facility, amount outstanding			70,000,000
Loan, principal amount outstanding		34,000,000
Loan maturity period		5
Loan, fixed interest rate		7.03%
Loan, amortization period (years)		25 years
Increase in interest rate due to default in repayment		5.00%
Loan, outstanding balance			104,053,000
Current portion of loans payable, Book Value			70,672,000	91,597,000
Long-term portion of loans payable, Book Value			33,381,000	32,133,000
Mutual Of Omaha Bank
Line of Credit Facility
Loan, outstanding balance			32,400,000
Current portion of loans payable, Book Value			600,000
Long-term portion of loans payable, Book Value			$ 31,800,000
Letter of Credit
Line of Credit Facility
Percentage of Letter of credit			2.75%