Fair Value of Financial Instruments (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 Equity securities	Dec. 31, 2011 Recurring Level 1	Dec. 31, 2011 Recurring Level 1 Equity securities	Dec. 31, 2012 Recurring Level 2	Dec. 31, 2011 Recurring Level 2	Dec. 31, 2012 Recurring Level 2 Interest rate cap	Dec. 31, 2011 Recurring Level 2 Interest rate cap	Dec. 31, 2011 Recurring Level 2 Natural Gas Hedge	Dec. 31, 2012 Recurring Total Fair Value	Dec. 31, 2011 Recurring Total Fair Value	Dec. 31, 2012 Recurring Total Fair Value Interest rate cap	Dec. 31, 2011 Recurring Total Fair Value Interest rate cap	Dec. 31, 2011 Recurring Total Fair Value Natural Gas Hedge	Dec. 31, 2011 Recurring Total Fair Value Equity securities
Fair value information
Trading securities			$ 12,369,000											$ 12,369,000
Available-for-sale securities			12,099,000											12,099,000
Total assets						12,000	432,000	4,050,000			12,000	432,000	4,050,000
Total assets		24,468,000		12,000	4,482,000				12,000	28,950,000
Derivative liabilities						6,615,000	5,683,000				6,615,000	5,683,000
Recorded loss related to trading securities still held	11,500,000
Realized losses on sale of available-for-sale securities	$ 1,600,000