Stock compensation (Tables)

3 Months Ended

Mar. 31, 2017

Stock Compensation

Schedule of valuation assumptions used for valuation of fair value of stock compensation granted

	Employee Stock Options For the Three Months Ended				Employee Stock Purchase Plan For the Three Months Ended
	March 31,				March 31,
	2017		2016		2017		2016
Average risk-free interest rates	1.82	%	1.50	%	1.27	%	0.73	%
Average expected life (in years)	5.36		5.00		0.25		0.25
Volatility	49	%	49	%	40	%	61	%
Weighted-average fair value (in dollars)	51.93		41.56		17.82		26.67

Schedule of option activity under the 2010 Stock Plan

		Shares Subject to
		Outstanding Options
	Shares Available		Weighted Average
	for Grant	Shares	Exercise Price
Balance at December 31, 2016	6,327,138	11,504,572	$	48.40
Options granted	(1,471,156)	1,471,156	$	114.41
Options exercised	—	(1,688,337)	$	26.42
Options cancelled	48,932	(48,932)	$	93.65
Balance at March 31, 2017	4,904,914	11,238,459	$	60.15

Schedule of RSU and PSU award activity under the 2010 Stock Plan

		Shares Subject to
	Shares Available	Outstanding Awards
	for Grant	Shares	Grant Date Value
Balance at December 31, 2016	1,146,152	1,246,570		—
RSUs granted	(68,782)	68,782	$	117.54
RSUs cancelled	15,341	(15,341)	$	83.64
RSUs released	—	(163,354)	$	118.45
PSUs released	—	(43,376)	$	122.29
Balance at March 31, 2017	1,092,711	1,093,281		—