Legal and Insurance Matters - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
0 Months Ended 3 Months Ended 12 Months Ended 0 Months Ended 1 Months Ended 3 Months Ended 12 Months Ended 3 Months Ended 0 Months Ended 12 Months Ended
Dec. 05, 2013
Dec. 31, 2013
Dec. 31, 2013
Jan. 07, 2014
Subsequent Event
Mar. 04, 2014
Subsequent Event
Mar. 31, 2013
2010 Derivative Action
Dec. 31, 2013
2010 Derivative Action
Dec. 31, 2013
2010 Class Action
Sep. 30, 2013
2010 Class Action
Oct. 07, 2013
2013 Shareholder Derivative Actions
LegalMatter
Defendant
Dec. 31, 2013
2013 Shareholder Derivative Actions
LegalMatter
Dec. 31, 2013
2013 Shareholder Class Actions
LegalMatter
Commitments and Contingencies Disclosure [Line Items]                        
Compensatory damages awarded $ 281.6     $ 163.8                
Surety Bonds   25.0 25.0                  
Available insurance limit   16.0 16.0                  
Reservation rights     9.0                  
Payment to Plaintiff's attorneys         13.5   0.3          
Issuance of shares to Plaintiffs attorneys             0.1          
Litigation expense   7.0       2.4 1.6 7.0 16.0      
Accrual for settlement offer                 16.0      
Stock to be issued for legal settlement, shares         0.8              
Stock to be issued for legal settlement, value         13.5              
Total value of settlement         $ 27.0              
Number of identical shareholder derivative lawsuits asserted                   2 3 2
Number of officers and directors in lawsuit                   10