Derivative Financial Instruments Activity of Hedging Instruments in Accumulated OCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Accumulated Net Gain (Loss) from Derivative Instruments Designated as Hedging Instruments [Member]	Dec. 31, 2012 Accumulated Net Gain (Loss) from Derivative Instruments Designated as Hedging Instruments [Member]	Jun. 30, 2012 Accumulated Net Gain (Loss) from Derivative Instruments Designated as Hedging Instruments [Member]	Dec. 31, 2011 Accumulated Net Gain (Loss) from Derivative Instruments Designated as Hedging Instruments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning of Period			$ (34,384)		$ (15,297)	$ (16,069)	$ (15,229)	$ (14,380)
Unrealized gain (loss) on derivative instruments	845	(849)	772	(849)
Accumulated Other Comprehensive Income (Loss), Net of Tax, End of Period	$ (57,929)		$ (57,929)		$ (15,297)	$ (16,069)	$ (15,229)	$ (14,380)