Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended |
Jun. 30, 2016 | Mar. 31, 2016 | Jun. 30, 2015 | Jun. 30, 2016 | Jun. 30, 2015 | Dec. 31, 2015 |
Stock-Based Compensation | | | | | | |
Expense incurred for stock-based compensation plans | $ 11.7 | | $ 10.1 | $ 23.2 | $ 20.2 | |
Expense incurred for stock-based compensation plans, net of tax | $ 8.9 | | 7.6 | $ 17.7 | 15.1 | |
2000 Employee Option Plan | | | | | | |
Stock-Based Compensation | | | | | | |
Number of additional stock options that can be granted (in shares) | | | | 0 | | |
Options exercisable period | | | | 10 years | | |
2009 Employee Option Plan | | | | | | |
Stock-Based Compensation | | | | | | |
Common Stock reserved for issuance | 58,000,000 | | | 58,000,000 | | |
Shares available for the granting of additional stock options | 11,965,910 | | | 11,965,910 | | |
Options exercisable period | | | | 10 years | | |
Options ratable vesting period | | | | 5 years | | |
2004 Directors Option Plan | | | | | | |
Stock-Based Compensation | | | | | | |
Shares available for the granting of additional stock options | 140,000 | | | 140,000 | | |
Options exercisable period | | | | 10 years | | |
Number of additional stock options expected to be granted (in shares) | 0 | | | 0 | | |
Stock Options | | | | | | |
Stock option activity | | | | | | |
Options outstanding at the beginning of the period (in shares) | 30,681,955 | 31,136,475 | | 31,136,475 | | |
Options granted (in shares) | 7,138,450 | 245,000 | | | | |
Options exercised (in shares) | (1,951,432) | (650,840) | | | | |
Options forfeited (in shares) | (389,400) | (48,680) | | | | |
Options outstanding at the end of the period (in shares) | 35,479,573 | 30,681,955 | | 35,479,573 | | 31,136,475 |
Vested and non-vested options expected to vest at the end of the period (in shares) | 33,088,422 | | | 33,088,422 | | |
Exercisable at the end of the period (in shares) | 16,569,063 | | | 16,569,063 | | |
Weighted Average Exercise Price | | | | | | |
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share) | $ 37.97 | $ 37.62 | | $ 37.62 | | |
Weighted average exercise price, options outstanding at the end of the period (in dollars per share) | 42.52 | $ 37.97 | | 42.52 | | $ 37.62 |
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share) | 41.88 | | | 41.88 | | |
Weighted average exercise price, exercisable (in dollars per share) | $ 31.50 | | | $ 31.50 | | |
Weighted Average Remaining Contractual Term | | | | | | |
Weighted average remaining contractual term of options outstanding | 7 years 3 months 7 days | 6 years 9 months | | | | 6 years 11 months 1 day |
Weighted average remaining contractual term of options vested options and non-vested expected to vest | 7 years 2 months 1 day | | | | | |
Weighted average remaining contractual term of options exercisable | 5 years 7 months 10 days | | | | | |
Aggregate Intrinsic Value | | | | | | |
Aggregate intrinsic value of options outstanding | $ 534.2 | $ 609.9 | | $ 534.2 | | $ 491 |
Aggregate intrinsic value of options, vested and non-vested options expected to vest | 518.8 | | | 518.8 | | |
Aggregate intrinsic value of options exercisable | $ 428.8 | | | $ 428.8 | | |
Status of the Company's non-vested options and changes during the year | | | | | | |
Non-vested options at the beginning of the period (in shares) | 17,474,960 | 17,323,040 | | 17,323,040 | | |
Non-vested options, options granted (in shares) | 7,138,450 | 245,000 | | | | |
Non-vested options, options vested (in shares) | (5,313,500) | (44,400) | | | | |
Non-vested options, options forfeited (in shares) | (389,400) | (48,680) | | | | |
Non-vested options at the end of the period (in shares) | 18,910,510 | 17,474,960 | | 18,910,510 | | 17,323,040 |
Weighted Average Fair Value at Grant Date | | | | | | |
Weighted average fair value at the grant date, options outstanding at the beginning of the period (in dollars per share) | $ 8.22 | $ 8.24 | | $ 8.24 | | |
Weighted average fair value at grant date, options granted (in dollars per share) | 7.40 | 6.98 | | | | |
Weighted average fair value at grant date, options vested (in dollars per share) | 7.91 | 9.82 | | | | |
Weighted average fair value at grant date, options forfeited (in dollars per share) | 8.33 | 8.38 | | | | |
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share) | $ 7.99 | $ 8.22 | | $ 7.99 | | $ 8.24 |
Fair Value at Grant Date | | | | | | |
Total intrinsic value of stock options exercised | $ 62 | | 32 | $ 82.6 | 57.9 | |
Total fair value of stock options vested | 42.1 | | $ 39.1 | 42.5 | $ 39.4 | |
Total compensation cost related to non-vested options not yet recognized | 133.3 | | | $ 133.3 | | |
Weighted average expected amortization period | | | | 3 years 8 months 1 day | | |
Restricted Shares | | | | | | |
Fair Value at Grant Date | | | | | | |
Total compensation cost related to non-vested restricted shares not yet recognized | $ 0.9 | | | $ 0.9 | | |
Weighted average expected amortization period | | | | 10 months 24 days | | |
Restricted Shares | 2012 Directors Restricted Stock Plan | | | | | | |
Stock-Based Compensation | | | | | | |
Shares available for the granting of additional stock options | 137,069 | | | 137,069 | | |
Restricted share activity | | | | | | |
Restricted shares outstanding at the beginning of the period (in shares) | 17,256 | 17,256 | | 17,256 | | |
Shares vested and issued (in shares) | (17,256) | | | | | |
Restricted shares granted | 16,905 | | | | | |
Restricted shares outstanding at the end of the period (in shares) | 16,905 | 17,256 | | 16,905 | | 17,256 |
Fair Value at Grant Date | | | | | | |
Fair value at the grant date, restricted shares outstanding at the beginning of the period (in dollars per share) | $ 57.97 | $ 57.97 | | $ 57.97 | | |
Fair value of restricted shares vested and issued (in dollar per share) | 57.97 | | | | | |
Fair value of restricted shares granted (in dollars per share) | 57.99 | | | | | |
Fair value at the grant date, restricted shares outstanding at the end of the period (in dollars per share) | $ 57.99 | $ 57.97 | | $ 57.99 | | $ 57.97 |
Weighted Average Remaining Amortization Term (in years) | | 1 month 24 days | | 10 months 24 days | | 4 months 21 days |