Long-term Debt and Derivatives (Details 2) (USD $)	9 Months Ended							1 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Senior secured credit facility	Dec. 31, 2011 Senior secured credit facility	Sep. 30, 2012 Revolving credit facility	Sep. 30, 2012 Variable rate Term Loan A	Sep. 30, 2012 Variable rate Term Loan B	Sep. 30, 2012 Other long-term obligations	Dec. 31, 2011 Other long-term obligations
Future minimum repayments of long-term debt
Within one year	$ 46,974,000
1-3 years	142,074,000
3-5 years	959,235,000
Over 5 years	1,029,732,000
Total minimum payments	2,178,015,000	2,044,914,000	1,840,875,000	1,715,750,000				10,000,000	1,949,000
Long-term Debt
Revolving credit facility amount outstanding					444,000,000
Term loan amount outstanding			24,100,000			656,300,000	740,600,000
Available borrowing capacity					231,900,000
Proceeds from other long-term Obligations	$ 10,000,000							$ 10,000,000