Derivative Instruments (Narrative) (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Apr. 30, 2011
Derivative Instruments
Derivative, Notional Amount				$ 50,000,000
Percentage of interest rate swap pays to counterparty				5.365%
Unrealized gain on interest rate swap, net of income tax	$ 0	$ 515,000	$ 1,334,000

Net of tax amount, before reclassification adjustments, of the change in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Also includes an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Reference 7: http://www.xbrl.org/2003/role/presentationRef

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