Equity (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	May 31, 2014	Apr. 30, 2014
2000 Employee Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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 [Line Items]
Common Stock reserved for issuance					58,000,000	32,000,000
Shares available for the granting of additional stock options	24,978,580
2000 Employee Option Plan and 2009 Employee Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options ratable vesting period	5 years
Options exercisable period	10 years
2004 Directors Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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 [Line Items]
Shares available for the granting of additional stock options	171,922
Stock option activity
Options outstanding at the beginning of the period (in shares)	26,880	32,858
Options granted (in shares)	18,340	26,880	32,858
Shares vested and issued (in shares)	(26,880)	(32,858)
Options outstanding at the end of the period (in shares)	18,340	26,880	32,858
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)	38.76	$ 26.63
Weighted average fair value at grant date, options granted (in dollars per share)	47.72	$ 38.76	$ 26.63
Weighted average fair value at grant date, options vested and issued (in dollars per share)	38.76	$ 26.63
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	47.72	$ 38.76	$ 26.63
Total compensation cost related to non-vested options not yet recognized (in dollars)	0.3
Weighted average expected amortization period	4 months 21 days	4 months 21 days	4 months 21 days
Stock Options
Stock option activity
Options outstanding at the beginning of the period (in shares)	26,844,452	26,893,438	28,033,800
Options granted (in shares)	6,220,000	5,576,000	5,980,000
Options exercised (in shares)	(4,790,252)	(5,272,426)	(6,505,922)
Options forfeited (in shares)	(486,280)	(352,560)	(614,440)
Options outstanding at the end of the period (in shares)	27,787,920	26,844,452	26,893,438	28,033,800
Vested and non-vested options expected to vest at the end of the period (in shares)	25,296,609
Exercisable at the end of the period (in shares)	11,347,360
Weighted Average Exercise Price
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share)	25.90	$ 21.70	$ 19.00
Weighted average exercise price, options granted (in dollars per share)	47.70	$ 39.00	$ 26.66
Weighted average exercise price, options exercised (in dollars per share)	20.27	$ 18.23	$ 14.66
Weighted average exercise price, options forfeited (in dollars per share)	34.55	$ 26.83	$ 21.42
Weighted average exercise price, options outstanding at the end of the period (in dollars per share)	31.60	$ 25.90	$ 21.70	$ 19.00
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share)	31.23
Weighted average exercise price, exercisable (in dollars per share)	23.16
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term of options outstanding	7 years 1 month 2 days	7 years 29 days	7 years 29 days	6 years 10 months 21 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 4 days
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding (in dollars)	617.2
Aggregate intrinsic value of options, vested and non-vested options expected to vest (in dollars)	571.3
Aggregate intrinsic value of options exercisable (in dollars)	347.8
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	16,033,842
Non-vested options, options granted (in shares)	6,220,000
Non-vested options, options vested (in shares)	(5,327,002)
Non-vested options, options forfeited (in shares)	(486,280)
Non-vested options at the end of the period (in shares)	16,440,560	16,033,842
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)	7.39
Weighted average fair value at grant date, options granted (in dollars per share)	8.64	$ 8.71	$ 6.48
Weighted average fair value at grant date, options vested (in dollars per share)	6.99
Weighted average fair value at grant date, options forfeited (in dollars per share)	7.81
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	7.98	$ 7.39
Total intrinsic value of stock options exercised (in dollars)	136.8	105.8	95.9
Total fair value of stock options vested (in dollars)	37.2	33.9	31.0
Total compensation cost related to non-vested options not yet recognized (in dollars)	95.6
Weighted average expected amortization period	3 years 4 months 24 days