Investment in and Advances to Unconsolidated Affiliate Affiliate Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2012
Investments in and Advances to Affiliates, Affiliate Balance Sheet [Abstract]
Equity Method Investment, Summarized Financial Information, Current Assets	$ 23,303	$ 24,943
Equity Method Investment-Property Plant & Equipment	122,371	130,868
Equity Method Investment, Summarized Financial Information, Noncurrent Assets	105,058	105,059
Equity Method Investment, Summarized Financial Information, Assets	250,732	260,870
Equity Method Investment, Summarized Financial Information, Current Liabilities	17,636	16,775
Equity Method Investment-Long-term Debt, Current Maturities	8,332	8,332
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities	22,085	26,584	$ 50,000
Investment Affiliate-Other Liabilities	75	83
Equity Method Investment Summarized Financial Information, Equity	202,604	209,096
Equity Method Investment, Summarized Financial Information, Liabilities and Equity	$ 250,732	$ 260,870