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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
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Dec. 31, 2013
Vested Stock Awards
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Dec. 31, 2012
Vested Stock Awards
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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
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| 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 | ||||||||||||||