Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions | Dec. 31, 2014 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014 | Dec. 31, 2014 |
Share-based Compensation Arrangement by Share-based Payment Award | | | | | | | | |
Expense incurred for stock-based compensation plans | | $ 11.8 | | | $ 10.1 | $ 32.1 | $ 29.4 | |
Expense incurred for stock-based compensation plans, net of tax | | $ 8.8 | | | 7.5 | $ 23.9 | 21.6 | |
Stock Options | | | | | | | | |
Stock option activity | | | | | | | | |
Options outstanding at the beginning of the period (in shares) | | 32,226,210 | 27,044,960 | 27,787,920 | | 27,787,920 | | |
Options granted (in shares) | | 112,000 | 6,286,200 | 92,000 | | | | |
Options exercised (in shares) | | (146,400) | (1,006,630) | (742,280) | | | | |
Options forfeited (in shares) | | (141,300) | (98,320) | (92,680) | | | | |
Options outstanding at the end of the period (in shares) | 27,787,920 | 32,050,510 | 32,226,210 | 27,044,960 | | 32,050,510 | | 27,787,920 |
Vested and non-vested options expected to vest at the end of the period (in shares) | | 29,433,574 | | | | 29,433,574 | | |
Exercisable at the end of the period (in shares) | | 14,625,670 | | | | 14,625,670 | | |
Weighted Average Exercise Price | | | | | | | | |
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share) | | $ 37.20 | $ 31.95 | $ 31.60 | | $ 31.60 | | |
Weighted average exercise price, options outstanding at the end of the period (in dollars per share) | $ 31.60 | 37.27 | $ 37.20 | $ 31.95 | | 37.27 | | $ 31.60 |
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share) | | 36.69 | | | | 36.69 | | |
Weighted average exercise price, exercisable (in dollars per share) | | $ 26.61 | | | | $ 26.61 | | |
Weighted Average Remaining Contractual Term | | | | | | | | |
Weighted average remaining contractual term of options outstanding | | 7 years 1 month 6 days | 7 years 4 months 2 days | 6 years 10 months 28 days | | | | 7 years 1 month 2 days |
Weighted average remaining contractual term of options vested options and non-vested expected to vest | | 7 years 4 days | | | | | | |
Weighted average remaining contractual term of options exercisable | | 5 years 6 months 7 days | | | | | | |
Aggregate Intrinsic Value | | | | | | | | |
Aggregate intrinsic value of options outstanding | $ 617.2 | $ 483.2 | $ 669.4 | $ 729.7 | | $ 483.2 | | $ 617.2 |
Aggregate intrinsic value of options, vested and non-vested options expected to vest | | 458.7 | | | | 458.7 | | |
Aggregate intrinsic value of options exercisable | | $ 356.1 | | | | $ 356.1 | | |
Status of the Company's non-vested options and changes during the year | | | | | | | | |
Non-vested options at the beginning of the period (in shares) | | 17,502,480 | 16,412,880 | 16,440,560 | | 16,440,560 | | |
Non-vested options, options granted (in shares) | | 112,000 | 6,286,200 | 92,000 | | | | |
Non-vested options, options vested (in shares) | | (48,340) | (5,098,280) | (27,000) | | | | |
Non-vested options, options forfeited (in shares) | | (141,300) | (98,320) | (92,680) | | | | |
Non-vested options at the end of the period (in shares) | 16,440,560 | 17,424,840 | 17,502,480 | 16,412,880 | | 17,424,840 | | 16,440,560 |
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) | | $ 8.24 | $ 7.99 | $ 7.98 | | $ 7.98 | | |
Weighted average fair value at grant date, options granted (in dollars per share) | | 7.65 | 8.49 | 10.30 | | | | |
Weighted average fair value at grant date, options vested (in dollars per share) | | 8.56 | 7.69 | 9.51 | | | | |
Weighted average fair value at grant date, options forfeited (in dollars per share) | | 8.13 | 8.09 | 7.94 | | | | |
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share) | $ 7.98 | $ 8.24 | $ 8.24 | $ 7.99 | | $ 8.24 | | $ 7.98 |
Fair Value at Grant Date | | | | | | | | |
Total intrinsic value of stock options exercised | | $ 3.9 | | | 45.5 | $ 61.8 | 123.9 | |
Total fair value of stock options vested | | 0.4 | | | $ 0.2 | 39.8 | $ 37.3 | |
Total compensation cost related to non-vested options not yet recognized | | 115.1 | | | | $ 115.1 | | |
Weighted average expected amortization period | | | | | | 3 years 6 months 18 days | | |
Restricted Shares | | | | | | | | |
Fair Value at Grant Date | | | | | | | | |
Total compensation cost related to non-vested restricted shares not yet recognized | | $ 0.6 | | | | $ 0.6 | | |
Weighted average expected amortization period | | | | | | 7 months 21 days | | |
2000 Employee Option Plan | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award | | | | | | | | |
Number of additional stock options that can be granted (in shares) | | 0 | | | | 0 | | |
Options exercisable period | | | | | | 10 years | | |
2009 Employee Option Plan | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award | | | | | | | | |
Common Stock reserved for issuance | | 58,000,000 | | | | 58,000,000 | | |
Shares available for the granting of additional stock options | | 18,820,680 | | | | 18,820,680 | | |
Options ratable vesting period | | | | | | 5 years | | |
Options exercisable period | | | | | | 10 years | | |
2004 Directors Option Plan | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award | | | | | | | | |
Shares available for the granting of additional stock options | | 140,000 | | | | 140,000 | | |
Number of additional stock options expected to be granted (in shares) | | 0 | | | | 0 | | |
Options exercisable period | | | | | | 10 years | | |
2012 Directors Restricted Stock Plan | | | | | | | | |
Share-based Compensation Arrangement by Share-based Payment Award | | | | | | | | |
Shares available for the granting of additional stock options | | 153,974 | | | | 153,974 | | |
2012 Directors Restricted Stock Plan | Restricted Shares | | | | | | | | |
Restricted share activity | | | | | | | | |
Restricted shares outstanding at the beginning of the period (in shares) | | 17,256 | 19,032 | 18,340 | | 18,340 | | |
Restricted shares vested and issued | | | (19,032) | | | | | |
Restricted shares granted | | | 17,256 | 692 | | | | |
Restricted shares outstanding at the end of the period (in shares) | 18,340 | 17,256 | 17,256 | 19,032 | | 17,256 | | 18,340 |
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 | $ 47.98 | $ 47.72 | | $ 47.72 | | |
Fair value of restricted shares vested and issued (in dollar per share) | | | 47.98 | | | | | |
Fair value of restricted shares granted (in dollars per share) | | | 57.97 | 54.96 | | | | |
Fair value at the grant date, restricted shares outstanding at the beginning of the period (in dollars per share) | $ 47.72 | $ 57.97 | $ 57.97 | $ 47.98 | | $ 57.97 | | $ 47.72 |
Weighted Average Remaining Amortization Term (in years) | 4 months 21 days | 7 months 21 days | 10 months 24 days | 1 month 24 days | | | | |