Employee Benefit Plans - Summary of Stock Options and Related Activity (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Options outstanding, shares
Options outstanding, Beginning balance	23,910,062
Granted	1,434,834
Exercised	(2,816,093)
Expired
Forfeited	(333,177)
Options outstanding, Ending balance	22,195,626	23,910,062
Options exercisable, Ending balance	15,745,500
Options Outstanding, Weighted Average Exercise Price
Options outstanding, weighted average exercise price, Beginning balance	$ 9.81
Granted	$ 24.03
Exercised	$ 9.55
Expired
Forfeited	$ 9.91
Options outstanding, Weighted average exercise price, Ending balance	$ 10.76	$ 9.81
Options exercisable, Weighted average exercise price, Ending balance	$ 9.87
Weighted-Average Remaining Contractual Term (Years)
Options outstanding, weighted average remaining contractual term (Years)	7 years 10 months 24 days	8 years
Options exercisable, weighted average remaining contractual term (Years)	7 years 9 months 18 days
Aggregate Intrinsic Value
Aggregate intrinsic value, Exercised	$ (40,918)
Options outstanding, aggregate intrinsic value	295,677
Options exercisable, aggregate intrinsic value	$ 223,821