Derivative financial instruments (Tables)

12 Months Ended

Dec. 31, 2011

Derivative financial instruments [Abstract]

Interest rate swaps

Information regarding interest swaps as of December 31, 2011 was as follows:

	Notional amount		Fair value of interest rate swaps		Increase in debt due to fair value adjustment
Fair value hedge related to long-term debt due in 2012	$	84,847	$	1,309	$	780
Fair value hedge related to long-term debt due in 2014		198,000		3,230		2,788
Total fair value hedges	$	282,847	$	4,539	$	3,568

Information regarding interest rate swaps as of December 31, 2010 was as follows:

	Notional amount		Fair value of interest rate swaps		Increase in debt due to fair value adjustment
Fair value hedge related to long-term debt due in 2012	$	210,000	$	5,456	$	4,879