Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Effective tax rate	21.20%	25.10%	21.70%
Tax items related to prior year tax adjustments		$ 1,793
Term of scheduled expiration of pioneer tax status certificates unless extensions are granted	2 years