Long-Term Debt - Additional Information (Details) $ in Thousands			9 Months Ended
	May. 16, 2014 USD ($)	Mar. 08, 2013 USD ($) Bank	Sep. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Jun. 20, 2011 USD ($)	Jul. 13, 2010 USD ($)	Dec. 31, 2009 USD ($)
Debt Instrument [Line Items]
Long-term debt, face amount			$ 25,000
Long-term debt, Amount Outstanding			615,367	$ 629,756
Senior Secured Notes, 7.25% [Member]
Debt Instrument [Line Items]
Long-term debt, face amount			$ 53,500
Long-term debt, stated interest rate			7.25%	7.25%
Long-term debt, Amount Outstanding			$ 44,969	$ 46,291
Senior Secured Notes, 6.47% [Member]
Debt Instrument [Line Items]
Long-term debt, face amount			$ 110,000
Long-term debt, stated interest rate			6.47%	6.47%
Long-term debt, Amount Outstanding			$ 102,650	$ 105,622
Senior Secured Notes, 8.50% [Member]
Debt Instrument [Line Items]
Long-term debt, face amount			$ 25,000
Long-term debt, stated interest rate			8.50%	8.50%
Long-term debt, Amount Outstanding			$ 19,063	$ 20,000
SDTS Credit Agreements | Senior Secured Notes, 7.25% [Member]
Debt Instrument [Line Items]
Long-term debt, face amount								$ 53,500
Long-term debt, stated interest rate								7.25%
SDTS Credit Agreements | Senior Secured Notes, 6.47% [Member]
Debt Instrument [Line Items]
Long-term debt, face amount							$ 110,000
Long-term debt, stated interest rate							6.47%
TDC [Member] | Senior Secured Notes, 8.50% [Member]
Debt Instrument [Line Items]
Long-term debt, face amount							$ 25,000
Long-term debt, stated interest rate							8.50%
Sharyland Projects, L.L.C [Member] | Senior Secured Credit Facilities [Member]
Debt Instrument [Line Items]
Long-term debt, face amount		$ 60,000
Construction-term loan		$ 447,000				$ 667,000
Number of banks, providing construction-term loan | Bank		14
Long-term debt, Amount Outstanding					$ 396,000
Construction term loan outstanding converted into term loan	$ 407,000
Sharyland Projects, L.L.C [Member] | Senior Secured Credit Facilities [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Interest rate			2.00%
Sharyland Projects, L.L.C [Member] | Senior Secured Credit Facilities [Member] | Period of Three Years [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Interest rate			2.25%
Sharyland Projects, L.L.C [Member] | Senior Secured Credit Facilities [Member] | Period After Three Years [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Interest rate			2.50%