Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011	Jan. 31, 2011	May 31, 2009
Derivative asset, notional amount											$ 50,000,000
Derivative, average fixed interest rate											7.75%
Derivative underlying hedge percent	80.00%				80.00%
Derivative, nonmonetary notional amount	5,000,000				5,000,000
Senior Notes	250,000,000				250,000,000				250,000,000	250,000,000
Reclassification of derivative gain (loss) to earnings	(143,000)	[1]	444,000	[1]	263,000	[1]	1,067,000	[1]
Fair value hedge liabilities	1,695,000				1,695,000
Fair value hedge assets									449,000
Senior notes interest rate	7.375%				7.375%					7.375%
Maximum [Member]
Fixed price range	3.29				3.29
Minimum [Member]
Fixed price range	2.65				2.65
Senior Notes [Member] | Fair Value, Inputs, Level 1 [Member]
Senior Notes	$ 250,000,000				$ 250,000,000

[1] Net of income tax (expense) benefit of $94 and $(295) for the three months ended June 30, 2012 and 2011, respectively, and $(175) and $(709) for the six months ended June 30, 2012 and 2011, respectively.