Fair Value Measurements (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Nonfinancial Assets and Nonfinancial Liabilities
Cost method investment	$ 2,200,000	$ 2,800,000	$ 3,000,000
Impairment charge	600,000	200,000
Level 3
Nonfinancial Assets and Nonfinancial Liabilities
Cost method investment	2,200,000	2,800,000
Carrying Amount
Fair Value Measurements
Long-term debt	347,267,000	363,300,000
Nonfinancial Assets and Nonfinancial Liabilities
Cost method investment	2,800,000	3,000,000
Fair Value
Fair Value Measurements
Long-term debt	$ 217,104,000	$ 319,788,000