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		$ 491.0
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	$ 62.0		32.0	$ 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