Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2011

Fair Value Measurements (Tables) [Abstract]

Assets and liabilities measured at fair value on a recurring basis

			Markets for		Observable		Unobservable
	December 31,		Identical Assets		Inputs		Inputs
	2011		(Level 1)		(Level 2)		(Level 3)
Deferred compensation plan investments	$	13,892	$	13,892	$	—	$	—
Total assets measured at fair value	$	13,892	$	13,892	$	—	$	—
Total liabilities measured at fair value	$	—	$	—	$	—	$	—

			Markets for		Observable		Unobservable
	December 31,		Identical Assets		Inputs		Inputs
	2010		(Level 1)		(Level 2)		(Level 3)
Deferred compensation plan investments	$	13,422	$	13,422	$	—	$	—
Total assets measured at fair value	$	13,422	$	13,422	$	—	$	—
Variable to fixed interest rate swaps	$	12,227	$	—	$	12,227	$	—
Variable to fixed natural gas swaps		226		—		226		—
Total liabilities measured at fair value	$	12,453	$	—	$	12,453	$	—