Long-term Debt - Summary of long-term debt (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Long-term debt, including current maturities	$ 2,890	$ 7,368
Long-term debt, current portion	(1,856)	(6,317)
Long-term debt, long-term portion	1,034	1,051
Notes payable- affiliated	420,338	469,268
Notes payable- affiliated, current portion	(323,491)	(323,476)
Notes payable- affiliated, long-term portion	96,847	145,792
Total long-term debt	97,881	146,843
Lines of credit
Debt Instrument [Line Items]
Long-term debt, including current maturities	1,000	2,000
Notes payable
Debt Instrument [Line Items]
Long-term debt, including current maturities	1,097	4,464
Equipment financing
Debt Instrument [Line Items]
Long-term debt, including current maturities	724	818
Other
Debt Instrument [Line Items]
Long-term debt, including current maturities	$ 69	$ 86