Accounting for Derivatives (Details) (Interest rate hedges, USD $)	3 Months Ended		3 Months Ended		6 Months Ended
	Jun. 30, 2013 Terminated hedge, May 2013	May 31, 2013 Terminated hedge, May 2013	Jun. 30, 2013 Designated as a hedging instrument	Jun. 30, 2012 Designated as a hedging instrument	Jun. 30, 2013 Designated as a hedging instrument	Jun. 30, 2012 Designated as a hedging instrument	Dec. 31, 2012 Designated as a hedging instrument	Jun. 30, 2013 Designated as a hedging instrument Intangible and other assets, net	Jun. 30, 2013 Designated as a hedging instrument Current portion of interest rate swaps	Dec. 31, 2012 Designated as a hedging instrument Current portion of interest rate swaps	Dec. 31, 2012 Designated as a hedging instrument Interest rate swaps
Accounting for Interest Rate Swap Agreements
Derivatives asset designated as hedging instruments, Fair value								$ 132,000
Derivatives liability designated as hedging instruments, Fair value		(8,800,000)							(3,276,000)	(3,873,000)	(6,043,000)
Total derivatives, Fair value			(3,144,000)		(3,144,000)		(9,916,000)
Notional amount of interest rate swaps		250,000,000	250,000,000		250,000,000
Pre-tax losses reclassified into interest expense	600,000
Weighted average effective fixed interest rate on interest rate swaps (as a percent)			1.70%		1.70%
Interest income recorded due to ineffectiveness related to interest rate swaps			200,000	0	200,000	0
Deferred losses to be reclassified during next 12 months	$ 3,800,000		$ 3,300,000		$ 3,300,000