v2.4.0.6
Overview and Basis of Presentation (Details Textual) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified
3 Months Ended 9 Months Ended
Oct. 31, 2012
Oct. 31, 2012
Summary of Significant Accounting Policies (Textual) [Abstract]    
Net proceeds $ 684,620,000 $ 684,620,000
Common Class A [Member] | IPO [Member]
   
Summary of Significant Accounting Policies (Textual) [Abstract]    
Issued and sold of common share   26.2
Offering price $ 28.00 $ 28.00
Net proceeds   684,600,000
Underwriting discounts and commissions   44,000,000
Approximate other offering expenses   $ 4,000,000
Common Class B [Member] | IPO [Member]
   
Summary of Significant Accounting Policies (Textual) [Abstract]    
Number of shares issued upon conversion   98.0
Number of shares issued upon converted   42.1