Equity, Stock Option and Restricted Shares (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
2000 Employee Option Plan
Stock-Based Compensation
Options exercisable period	10 years
2009 Employee Option Plan
Stock-Based Compensation
Number of additional stock options that will be granted (in shares)	0
Options ratable vesting period	5 years
Options exercisable period	10 years
2017 Employee Option Plan
Stock-Based Compensation
Common Stock reserved for issuance	30,000,000
Shares available for the granting of additional stock options	22,991,400
Options ratable vesting period	5 years
Options exercisable period	10 years
2004 Directors Option Plan
Stock-Based Compensation
Options exercisable period	10 years
Stock Options
Stock option activity
Options outstanding at the beginning of the period (in shares)	32,266,391	31,136,475	27,787,920
Options granted (in shares)	7,029,600	7,560,450	6,490,200
Options exercised (in shares)	(5,773,287)	(5,703,254)	(2,718,745)
Options forfeited (in shares)	(300,340)	(727,280)	(422,900)
Options outstanding at the end of the period (in shares)	33,222,364	32,266,391	31,136,475	27,787,920
Vested and non-vested options expected to vest at the end of the period (in shares)	31,214,883
Exercisable at the end of the period (in shares)	13,621,924
Weighted Average Exercise Price
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share)	$ 44.14	$ 37.62	$ 31.60
Weighted average exercise price, options granted (in dollars per share)	72.98	57.72	57.85
Weighted average exercise price, options exercised (in dollars per share)	31.87	25.80	23.71
Weighted average exercise price, options forfeited (in dollars per share)	55.16	50.17	41.73
Weighted average exercise price, options outstanding at the end of the period (in dollars per share)	52.27	$ 44.14	$ 37.62	$ 31.60
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share)	51.61
Weighted average exercise price, exercisable (in dollars per share)	$ 39.48
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term of options outstanding	7 years 18 days	7 years 11 days	6 years 11 months 1 day	7 years 1 month 2 days
Weighted average remaining contractual term of options vested options and non-vested expected to vest	6 years 11 months 16 days
Weighted average remaining contractual term of options exercisable	5 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding	$ 1,180.3
Aggregate intrinsic value of options, vested and non-vested options expected to vest	1,129.8
Aggregate intrinsic value of options exercisable	$ 658.2
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	18,725,570
Options granted (in shares)	7,029,600	7,560,450	6,490,200
Non-vested options, options vested (in shares)	(5,854,390)
Non-vested options, options forfeited (in shares)	(300,340)
Non-vested options at the end of the period (in shares)	19,600,440	18,725,570
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)	$ 7.99
Weighted average fair value at grant date, options granted (in dollars per share)	8.78	$ 7.39	$ 8.47
Weighted average fair value at grant date, options vested (in dollars per share)	7.91
Weighted average fair value at grant date, options forfeited (in dollars per share)	8.10
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 8.29	$ 7.99
Fair Value at Grant Date
Total intrinsic value of stock options exercised (in dollars)	$ 268.7	$ 197.2	$ 88.1
Total fair value of stock options vested (in dollars)	46.3	$ 43.1	$ 39.9
Total compensation cost related to non-vested options not yet recognized (in dollars)	$ 120.3
Weighted average expected amortization period	3 years 3 months 18 days
Restricted Shares | 2012 Directors Restricted Stock Plan
Stock-Based Compensation
Shares available for the granting of additional stock options	124,164
Restricted share activity
Restricted shares outstanding at the beginning of the period (in shares)	16,905	17,256	18,340
Restricted shares granted (in shares)	12,905	16,905	17,948
Shares vested and issued (in shares)	(16,905)	(17,256)	(19,032)
Restricted shares outstanding at the end of the period (in shares)	12,905	16,905	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)	$ 57.99	$ 57.97	$ 47.72
Fair value of restricted shares vested and issued (in dollar per share)	57.99	57.97	47.98
Fair value of restricted shares granted (in dollars per share)	73.25	57.99	57.85
Fair value at the grant date, restricted shares outstanding at the end of the period (in dollars per share)	$ 73.25	$ 57.99	$ 57.97	$ 47.72
Weighted Average Remaining Amortization Term (in years)	4 months 13 days	4 months 17 days	4 months 21 days	4 months 21 days
Total fair value of restricted share awards vested (in dollars)	$ 1.0	$ 1.0	$ 0.9
Total compensation cost related to non-vested restricted shares not yet recognized (in dollars)	$ 0.4
Weighted average expected amortization period	4 months 13 days