Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	May 31, 2014	Apr. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award
Expense incurred for stock-based compensation plans (in dollars)	$ 10.1	$ 9.3
Expense incurred for stock-based compensation plans, net of tax (in dollars)	7.6	6.8
Stock Options
Stock option activity
Options outstanding at the beginning of the period (in shares)	27,787,920		27,787,920
Options granted (in shares)	92,000
Options exercised (in shares)	(742,280)
Options forfeited (in shares)	(92,680)
Options outstanding at the end of the period (in shares)	27,044,960
Vested and non-vested options expected to vest at the end of the period (in shares)	24,835,981
Exercisable at the end of the period (in shares)	10,632,080
Weighted Average Exercise Price
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share)	$ 31.60		$ 31.60
Weighted average exercise price, options outstanding at the end of the period (in dollars per share)	$ 31.95
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share)	$ 31.54
Weighted average exercise price, exercisable (in dollars per share)	$ 23.32
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term of options outstanding	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	6 years 9 months 29 days
Weighted average remaining contractual term of options exercisable	5 years 3 months 26 days
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding (in dollars)	729.7		617.2
Aggregate intrinsic value of options, vested and non-vested options expected to vest (in dollars)	680.2
Aggregate intrinsic value of options exercisable (in dollars)	378.6
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	16,440,560		16,440,560
Non-vested options, options granted (in shares)	92,000
Non-vested options, options vested (in shares)	(27,000)
Non-vested options, options forfeited (in shares)	(92,680)
Non-vested options at the end of the period (in shares)	16,412,880
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)	$ 7.98		$ 7.98
Weighted average fair value at grant date, options granted (in dollars per share)	$ 10.30
Weighted average fair value at grant date, options vested (in dollars per share)	$ 9.51
Weighted average fair value at grant date, options forfeited (in dollars per share)	$ 7.94
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 7.99
Total intrinsic value of stock options exercised (in dollars)	25.9	15.6
Total fair value of stock options vested (in dollars)	0.3	0.1
Total compensation cost related to non-vested options not yet recognized (in dollars)	$ 87.4
Weighted average expected amortization period	3 years 3 months 4 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
2009 Employee Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
Common Stock reserved for issuance				58,000,000	32,000,000
Shares available for the granting of additional stock options	24,979,260
2000 Employee Option Plan and 2009 Employee Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
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
Options ratable vesting period	3 years
Options exercisable period	10 years
Number of additional stock options expected to be granted (in shares)	0
2012 Directors Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares available for the granting of additional stock options	171,230
Stock option activity
Options outstanding at the beginning of the period (in shares)	18,340		18,340
Options granted (in shares)	692
Options outstanding at the end of the period (in shares)	19,032
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)	$ 47.72		$ 47.72
Weighted average fair value at grant date, options granted (in dollars per share)	$ 4.96
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 47.98
Weighted average expected amortization period	1 month 24 days		4 months 21 days