Summary of Significant Accounting Policies (Details Textual) (USD $)	0 Months Ended	9 Months Ended		1 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended		9 Months Ended
	May 05, 2014	Sep. 30, 2014	Sep. 30, 2014 Customer receivables concentration Net receivable Rail Group customer	Sep. 30, 2014 Current repurchase program	Mar. 31, 2014 Current repurchase program	Sep. 30, 2014 Current repurchase program	Sep. 30, 2014 Current repurchase program	Sep. 30, 2013 Prior repurchase program	Sep. 30, 2013 Prior repurchase program	Sep. 30, 2014 Prior repurchase program	Sep. 30, 2014 Common Stock
Summary of Significant Accounting Policies (Textual) [Abstract]
Stock split conversion ratio	2
Adjustments to Additional Paid in Capital, Stock Split		$ 0									$ 78,000,000
Authorized amount from board of directors for share repurchase				250,000,000		250,000,000	250,000,000			200,000,000
Share repurchase program expiry date					Dec. 31, 2015
Shares repurchased under the program (in shares)						407,100	747,246	1,079,882	3,668,378
Cost of shares repurchased		31,500,000				19,000,000	31,500,000	23,900,000	73,800,000
Shares repurchased settled in subsequent month				$ 2,700,000
Number of customers			1
Net receivables percentage			10.00%