Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Detail)

v2.4.0.8
Share-Based Compensation - Summary of Activity Under Share-Based Compensation Plans (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 9 Months Ended
Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Awards Outstanding, Beginning Balance 11,333,000
Granted, Awards 85,000
Exercised, Awards (10,000)
Forfeited, Awards (28,000)
Awards Outstanding, Ending Balance 11,380,000
Awards Exercisable, Ending Balance 7,590,000
Weighted Average Exercise Price Outstanding, Beginning Balance $ 28.62
Granted, Weighted Average Exercise Price $ 35.46
Exercised, Weighted Average Exercise Price $ 9.07
Forfeited, Weighted Average Exercise Price $ 44.23
Weighted Average Exercise Price Outstanding, Ending Balance $ 28.65
Exercisable, Weighted Average Exercise Price, Ending Balance $ 20.82
Weighted Average Remaining Contractual Term Outstanding, Beginning Balance 5 years 10 months 24 days
Weighted Average Remaining Contractual Term Outstanding, Ending Balance 5 years 1 month 6 days
Exercisable, Weighted Average Remaining Contractual Term, Ending Balance 4 years 1 month 6 days
Aggregate Intrinsic Value Outstanding, Beginning balance $ 119.1
Aggregate Intrinsic Value Outstanding, Ending balance 467.9
Exercisable, Aggregate Intrinsic Value, Ending Balance $ 371.5
Incentive Plan and Independent Directors Stock Units [Member]
  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Outstanding and non-vested at December 31, 2012, Shares 321,600
Granted, Shares 7,600
Vested, Shares (193,500)
Forfeited, Shares (200)
Outstanding and non-vested at September 30, 2013, Shares 135,500
Outstanding and non-vested at December 31, 2012, Weighted Average Grant Date Fair Value $ 11.70
Granted, Weighted Average Grant Date Fair Value $ 35.63
Vested, Weighted Average Grant Date Fair Value $ 13.84
Forfeited, Weighted Average Grant Date Fair Value $ 53.60
Outstanding and non-vested at September 30, 2013, Weighted Average Grant Date Fair Value $ 9.91