Long-Term Debt -Interest Rate Caps (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivative [Line Items]
Interest Rate Cap, cap rate	3.50%
Interest Rate Cap, fair value	$ 0.1	$ 0.7
Cap agreement effective January 14, 2011-2013 [Member]
Derivative [Line Items]
Interest Rate Cap, number of agreements	4
Interest Rate Cap, notional amount	1,100.0
Cap agreement effective January 14, 2013-2015 [Member]
Derivative [Line Items]
Interest Rate Cap, number of agreements	4
Interest Rate Cap, notional amount	$ 500.0
Minimum [Member]
Derivative [Line Items]
Interest Rate Cap, hedge percent requirement	50.00%