Derivative Instruments and Hedging Activities - Amounts included in Accumulated Other Comprehensive Loss (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Amounts included in accumulated other comprehensive income for derivatives designated as hedging instruments
Accumulated other comprehensive (loss) income, fair value, net of taxes	$ (1,136)	$ (1,241)
Interest rate swap [Member] | Cash flow hedge [Member]
Amounts included in accumulated other comprehensive income for derivatives designated as hedging instruments
Accumulated other comprehensive (loss) income, fair value, net of taxes	$ (1,136)	$ (1,241)