Stock-based Awards (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended			0 Months Ended	1 Months Ended
	Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 01, 2015	Jan. 31, 2014
Number of Options
Outstanding at the end of the period (in shares)		25,589,876
Common stock
Additional disclosure
Share Price		$ 22.90
Options
Number of Options
Outstanding at the beginning of period (in shares)		18,363,144				18,363,144
Granted (in shares)		11,076,585
Exercised (in shares)		(2,751,389)
Canceled/forfeited (in shares)		(1,098,464)
Outstanding at the end of the period (in shares)		25,589,876	18,363,144
Vested and expected to vest at the end of the period (in shares)		24,572,090
Exercisable at the end of the period (in shares)		18,291,866
Weighted-Average Exercise Price
Outstanding at the beginning of period (in dollars per share)		$ 4.89				4.89
Granted (in dollars per share)		$ 15.99
Exercised (in dollars per share)		$ 2.15
Canceled/forfeited (in dollars per share)		$ 9.66
Outstanding at the end of the period (in dollars per share)		$ 9.79	$ 4.89
Vested and expected to vest at the end of the period (in dollars per share)		$ 9.73
Exercisable at the end of the period (in dollars per share)		$ 9.12
Weighted Average Remaining Contract Life (in years)
Outstanding at the end of the period		7 years 6 months 18 days	7 years 2 months 1 day
Vested and expected to vest at the end of the period		7 years 5 months 27 days
Exercisable at the end of the period		6 years 11 months 19 days
Aggregate Intrinsic Value
Intrinsic value of all outstanding options		$ 365.0
Intrinsic value of options vested and expected to vest		353.0
Intrinsic value of exercisable options		281.5
Additional disclosure
Remaining stock-based compensation expense for unvested awards		62.5
Weighted average period over which remaining stock based compensation expense for unvested awards is expected to be recognized		2 years 9 months 15 days
Weighted-average grant-date fair value per share of options granted (in dollars per share)		$ 6.32	$ 4.79	$ 4.83
Stock-based compensation expense		27.2	8.9	9.4
Intrinsic value of options exercised		57.1	0.6	2.9
Excess tax benefits realized for the tax deductions from stock options exercised		0	0	0
Additional stock compensation as a result of the modification				4.5
Accelerated vesting of stock options to purchase shares of common stock (in shares)	726,469
Options | Stock Options Performance
Number of Options
Granted (in shares)			1,765,875
Weighted-Average Exercise Price
Granted (in dollars per share)			$ 8.85
Additional disclosure
Grant date fair values		$ 20.1	$ 8.8	$ 0.8
Options | Stock Options Performance 1
Number of Options
Granted (in shares)			82,327
Options | Stock Options Performance 2
Number of Options
Granted (in shares)		2,776,114	1,683,548
Outstanding at the end of the period (in shares)		2,241,796
Weighted-Average Exercise Price
Granted (in dollars per share)		$ 12.81
Outstanding at the end of the period (in dollars per share)		$ 12.81
Additional disclosure
Vesting period					48 months	48 months
Options | Certain executives | Stock Options Performance 1
Number of Options
Granted (in shares)				166,665
Weighted-Average Exercise Price
Granted (in dollars per share)				$ 11.51
Options | Former executive
Additional disclosure
Accelerated vesting of stock options to purchase shares of common stock (in shares)	631,333