Annual report pursuant to Section 13 and 15(d)

Share-based Compensation - Additional Information (Detail)

v2.4.0.8
Share-based Compensation - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2009
Dec. 31, 2013
Restricted Stock
Dec. 31, 2013
Vested Stock Awards
Dec. 31, 2012
Vested Stock Awards
Dec. 31, 2013
Performance Based Restricted Stock
Restricted Stock
Dec. 31, 2012
Performance Based Restricted Stock
Restricted Stock
Dec. 31, 2013
Time Based Restricted Stock
Restricted Stock
Aug. 24, 2011
MTS
Employee
Aug. 24, 2011
MTS
Maximum
Aug. 24, 2011
MTS
Vesting over first year
Aug. 24, 2011
MTS
Vesting over last three years
Dec. 31, 2013
Board of Directors Policy
Dec. 31, 2009
Vesting on the 16th quarter
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                                
Stock options vesting period 4 years     4 years 4 years     2 years     4 years       4 years  
Expiration period from grant date 10 years                     10 years        
Percentage of stock options to be vested over 15 quarters       75.00%                        
Percentage of stock options to be vested during remaining period                         25.00% 20.00%   25.00%
Stock options granted                     349,693          
Number of employees authorized for grant                     96          
Weighted average grant-date fair value of options granted $ 10.37 $ 9.78 $ 11.87                          
Aggregate intrinsic value of stock options $ 23.3 $ 42.7 $ 68.6                          
Aggregate intrinsic value, outstanding 32.1 49.9                            
Aggregate intrinsic value of options exercisable 18.8 29.9                            
Unrecognized non-vested stock options 35.4 28.0                            
Unrecognized non-vested stock awards recognition period 2 years 9 months 18 days 2 years 8 months 12 days             0 years 2 years 7 months 6 days            
Total number of stock options vested during the period 5,864,340 5,821,461       1,295,116 1,349,016                  
Fair value of stock options vested during the period           30.3 29.1                  
Unrecognized compensation cost               0   40.5            
Aggregate intrinsic Value of awards               $ 1.6   $ 48.9