Accounting for Shared-Based Payments (Details 2) (Stock options, USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended		12 Months Ended	3 Months Ended
	Jan. 17, 2013 Callisto	Mar. 31, 2013 Callisto	Dec. 31, 2012 Exercise price per Share 0.50 - 5.20	Mar. 31, 2013 Exercise price per Share 0.44 - 20.01	Mar. 31, 2013 Exercise price per Share 0.44 - 20.01 Maximum	Mar. 31, 2013 Exercise price per Share 0.44 - 20.01 Minimum	Mar. 31, 2013 Exercise price per Share 0.50 - 4.28	Mar. 31, 2013 Exercise price per Share 4.42
Shared-based payments
Options outstanding (in shares)			9,734,268	10,449,232
Granted (in shares)	1,221,316			1,249,316
Exercised (in shares)							(34,352)
Forfeited (in shares)								(500,000)
Exercisable at the end of the period (in shares)				3,917,662
Exercise Price Per Share
Exercise price, low end of the range (in dollars per share)			$ 0.50	$ 0.44			$ 0.50
Exercise price, high end of the range (in dollars per share)			$ 5.20	$ 20.01			$ 4.28
Granted (in dollars per share)					$ 20.01	$ 0.44
Forfeited (in dollars per share)								$ 4.42
Exercisable at the end of the period (in dollars per share)					$ 20.01	$ 0.44
Weighted average exercise price per share of outstanding options (in dollars per share)			$ 2.75	$ 3.33
Granted (in dollars per share)				$ 8.29
Exercised (in dollars per share)							$ 3.04
Forfeited (in dollars per share)								$ 4.42
Exercisable at the end of the period (in dollars per share)				$ 3.09
Intrinsic Value
Intrinsic value of options outstanding (in dollars)			$ 24,482	$ 32,466
Intrinsic value of options exercisable (in dollars)				$ 14,136
Weighted Average Remaining Contractual Term
Balance at the end of the period			6 years 5 months 12 days	7 years 4 days
Exercisable at the end of the period				5 years 3 months 18 days
Additional disclosures
Vested (in shares)		1,010,026