Derivative Financial Instruments (Details 2) (Designated as cash flow hedging instruments, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Entity's derivative instruments within the condensed consolidated balance sheets
Asset derivatives	$ 9	$ 12
Liability derivatives	5,546	6,615
Interest rate cap
Entity's derivative instruments within the condensed consolidated balance sheets
Asset derivatives	9	12
Interest rate cap | Other current assets
Entity's derivative instruments within the condensed consolidated balance sheets
Asset derivatives	7	8
Interest rate cap | Other long-term assets
Entity's derivative instruments within the condensed consolidated balance sheets
Asset derivatives	2	4
Interest rate swaps
Entity's derivative instruments within the condensed consolidated balance sheets
Liability derivatives	5,546	6,615
Interest rate swaps | Other current liabilities
Entity's derivative instruments within the condensed consolidated balance sheets
Liability derivatives	4,100	4,100
Interest rate swaps | Other long-term liabilities
Entity's derivative instruments within the condensed consolidated balance sheets
Liability derivatives	$ 1,400	$ 2,500