Equity based compensation (Summary of non-vested stock awards and stock option awards) (Details) (USD $)	0 Months Ended	9 Months Ended
	Aug. 14, 2013	Sep. 30, 2013
Nonvested Stock [Member]
Nonvested Stock and Restricted Stock Units, Number of shares outstanding (in shares):
Beginning balance		396,073
Granted	42,858	589,102
Vested		(366,856)
Ending balance		618,319
Nonvested Stock and Restricted Stock Units, Weighted average grant date fair value (in dollars per share):
Beginning balance		$ 1.06
Granted		$ 16.78
Vested		$ 0.93
Ending balance		$ 16.11
Restricted Stock Units [Member]
Nonvested Stock and Restricted Stock Units, Number of shares outstanding (in shares):
Beginning balance		0
Granted	10,000	10,000
Vested		0
Ending balance		10,000
Nonvested Stock and Restricted Stock Units, Weighted average grant date fair value (in dollars per share):
Beginning balance		$ 0.00
Granted		$ 13.96
Vested		$ 0.00
Ending balance		$ 13.96
Stock Option [Member]
Nonvested Stock and Restricted Stock Units, Number of shares outstanding (in shares):
Granted	463,106
Stock Options, Number of options outstanding (in shares):
Beginning balance		772,851
Granted		463,106
Exercised		(546,244)
Ending balance		689,713
Stock Options, Weighted average exercise price (in dollars per share):
Beginning balance		$ 0.97
Granted		$ 14.00
Exercised		$ 0.97
Ending balance	$ 14.00	$ 9.72