Derivative Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Derivatives [Line Items]
Net unrealized gain/(loss) on qualifying cash flow hedges, net of tax	$ 1,334	$ (1,590)	$ 3,991
Interest rate swap agreement [Member]
Derivatives [Line Items]
Net unrealized gain/(loss) on qualifying cash flow hedges, net of tax	$ 1,334	$ (1,590)