Related Party Transactions (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 27, 2013
Related Party Transactions [Abstract]
Percentage of equity interest (in hundredths)	19.90%			19.90%
Amount of equity investment	$ 1,700,000	$ 1,200,000		$ 1,600,000
Equity in earnings of limited partnership	(868,000)	(914,000)	(816,000)
Cash distribution from earnings of related party	400,000	1,600,000	1,000,000
Purchases from W&B	3,700,000	23,100,000	19,500,000
Maintenance and repair services, accessories and parts invoiced from related party	1,500,000	1,300,000	1,600,000
Due to related parties	$ 400,000	$ 300,000