Stock compensation (Details 2) - Stock options and awards	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Shares Available For Grant
Outstanding at the beginning of the period (in shares)	5,399,816
Options granted (in shares)	(1,864,485)
Options cancelled (in shares)	318,876
Outstanding at the end of the period (in shares)	3,854,207
Number Outstanding
Outstanding at the beginning of the period (in shares)	14,655,043
Options granted (in shares)	1,864,485
Options exercised (in shares)	(4,574,951)
Options cancelled (in shares)	(318,876)
Outstanding at the end of the period (in shares)	11,625,701
Weighted Average Exercise Price per share
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 21.96
Options granted (in dollars per share) | $ / shares	78.40
Options exercised (in dollars per share) | $ / shares	16.51
Options cancelled (in dollars per share) | $ / shares	44.38
Outstanding at the end of the period (in dollars per share) | $ / shares	$ 32.55