Summary of Significant Accounting Policies (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Summary of Significant Accounting Policies (Textual) [Abstract]
Authorized amount from board of directors for share repurchase	$ 200,000,000
Share repurchase program effective date - current plan	Oct. 01, 2012	Oct. 01, 2012		Oct. 01, 2012
Share repurchase program expiry date - current plan	Dec. 31, 2014	Dec. 31, 2014		Dec. 31, 2014
Stock repurchase program expiry date - expired plan	Sep. 30, 2012	Sep. 30, 2012		Sep. 30, 2012
Number of shares repurchased		141,992	0	1,834,221	0
Cost of shares repurchased		4,000,000		45,200,000
Net receivables from a single customer in Energy Equipment Group	22.00%	22.00%		22.00%
Maximum period that sale from lease fleet is recorded as revenue						1 year
Minimum period after which sale from lease fleet is recognized as net gain or loss						1 year
Decrease in revenue from reclassification adjustments of prior period			$ 5,700,000		$ 17,900,000