Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended			6 Months Ended		12 Months Ended
	Dec. 31, 2014	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 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		$ 10.1		$ 10.0	$ 20.2	$ 19.2
Expense incurred for stock-based compensation plans, net of tax		$ 7.6		7.3	$ 15.1	14.1
Stock Options
Stock option activity
Options outstanding at the beginning of the period (in shares)		27,044,960	27,787,920		27,787,920
Options granted (in shares)		6,286,200	92,000
Options exercised (in shares)		(1,006,630)	(742,280)
Options forfeited (in shares)		(98,320)	(92,680)
Options outstanding at the end of the period (in shares)	27,787,920	32,226,210	27,044,960		32,226,210		27,787,920
Vested and non-vested options expected to vest at the end of the period (in shares)		29,356,675			29,356,675
Exercisable at the end of the period (in shares)		14,723,730			14,723,730
Weighted Average Exercise Price
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share)		$ 31.95	$ 31.60		$ 31.60
Weighted average exercise price, options outstanding at the end of the period (in dollars per share)	$ 31.60	37.20	$ 31.95		37.20		$ 31.60
Weighted average exercise price, vested and non-vested options expected to vest (in dollars per share)		36.63			36.63
Weighted average exercise price, exercisable (in dollars per share)		$ 26.58			$ 26.58
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term of options outstanding		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 3 months
Weighted average remaining contractual term of options exercisable					5 years 9 months 4 days
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding	$ 617.2	$ 669.4	$ 729.7		$ 669.4		$ 617.2
Aggregate intrinsic value of options, vested and non-vested options expected to vest		626.5			626.5
Aggregate intrinsic value of options exercisable		$ 462.2			$ 462.2
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)		16,412,880	16,440,560		16,440,560
Non-vested options, options granted (in shares)		6,286,200	92,000
Non-vested options, options vested (in shares)		(5,098,280)	(27,000)
Non-vested options, options forfeited (in shares)		(98,320)	(92,680)
Non-vested options at the end of the period (in shares)	16,440,560	17,502,480	16,412,880		17,502,480		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)		$ 7.99	$ 7.98		$ 7.98
Weighted average fair value at grant date, options granted (in dollars per share)		8.49	10.30
Weighted average fair value at grant date, options vested (in dollars per share)		7.69	9.51
Weighted average fair value at grant date, options forfeited (in dollars per share)		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	$ 7.99		$ 8.24		$ 7.98
Fair Value at Grant Date
Total intrinsic value of stock options exercised		$ 32.0		62.9	$ 57.9	78.5
Total fair value of stock options vested		39.1		$ 36.9	39.4	$ 37.1
Total compensation cost related to non-vested options not yet recognized		123.8			$ 123.8
Weighted average expected amortization period					3 years 8 months 27 days
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
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
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		18,791,380			18,791,380
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			140,000
Number of additional stock options expected to be granted (in shares)		0			0
Options ratable vesting period					3 years
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)		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	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)		$ 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	$ 47.98		$ 57.97		$ 47.72
Weighted Average Remaining Amortization Term (in years)	4 months 21 days	10 months 24 days	1 month 24 days
Fair value of restricted shares granted (in dollars per share)		$ 57.97	$ 54.96