Stock-Based Compensation - Summary of Changes in Stock Options Outstanding (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Weighted average exercise price (in dollars per share):
Options exercisable as of March 31, 2014	$ 11.00
Employee Stock Option
Number of Options (in shares):
Options outstanding as of December 31, 2013	2.6
Granted	0.4
Exercised	0
Canceled	(1.1)
Options outstanding as of March 31, 2014	1.9	2.6
Options exercisable as of March 31, 2014	0.9
Options outstanding, weighted average remaining contract term (in years)	7 years 8 months 12 days	4 years 2 months 12 days
Options exercisable, Weighted average remaining contract term (in years)	6 years 7 months 6 days
Weighted average exercise price (in dollars per share):
Options outstanding as of December 31, 2013	$ 10.46
Granted	$ 16.03
Exercised	$ 0.00
Canceled	$ 9.04
Options outstanding as of March 31, 2014	$ 12.62	$ 10.46
Aggregate Intrinsic Value:
Options outstanding as of December 31, 2013	$ 17.8
Exercised	0
Options outstanding as of March 31, 2014	0	17.8
Options exercisable as of March 31, 2014	$ 0