Stockholders' equity, share-based compensation arrangements by share-based payment award (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) Plan $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $	$ 15,848,000	$ 12,829,000	$ 11,238,000
Aggregate intrinsic value [Abstract]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 10 months 24 days
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options | $	$ 20,000,000
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense | $	15,848,000	12,829,000	$ 11,238,000
Stock Options [Member]
Aggregate Intrinsic Value [Abstract]
Outstanding, beginning of period | $	29,181,534
Outstanding, end of period | $	52,324,284	$ 29,181,534
Exercisable, end of period | $	31,006,178
Options expected to vest, end of period | $	$ 17,043,405
Aggregate intrinsic value [Abstract]
Weighted average remaining contractual term of options outstanding	4 years 4 months 24 days	4 years
Weighted average remaining contractual term of options exercisable	3 years 4 months 24 days	3 years 2 months 12 days
Weighted average grant date fair value of options granted (in dollars per share) | $ / shares	$ 8.66	$ 8.84	$ 5.38
Total intrinsic value of options exercised | $	$ 20,200,000	$ 7,500,000	$ 6,900,000
Total fair value of awards vested | $	$ 14,400,000	$ 12,300,000	9,100,000
2006 Plan [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for issuance under the plan (in shares)	15,200,000.0
Options outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	3,837,993
Granted (in shares)	690,221
Exercised (in shares)	(1,360,955)
Forfeited (in shares)	(189,439)
Outstanding, end of period (in shares)	2,977,820	3,837,993
Exercisable, end of period (in shares)	1,442,178
Options expected to vest, end of period (in shares)	1,195,677
Weighted-Average Exercise Price [Roll Forward]
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 20.04
Granted (in dollars per share) | $ / shares	29.03
Exercised (in dollars per share) | $ / shares	18.09
Forfeited (in dollars per share) | $ / shares	24.29
Outstanding, end of period (in dollars per share) | $ / shares	22.74	$ 20.04
Exercisable, end of period (in dollars per share) | $ / shares	19.12
Options expected to vest, end of period (in dollars per share) | $ / shares	$ 25.76
2006 Plan [Member] | Stock Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that may be granted per year to a single participant (in shares)		1.0
2006 Plan [Member] | Restricted Stock Units (RSUs) [Member]
Restricted stock unit award activity [Roll Forward]
Outstanding, beginning of period (in shares)	927,356
Granted (in shares)	473,111
Vested (in shares)	(422,515)
Forfeited (in shares)	(82,156)
Outstanding, end of period (in shares)	895,796	927,356
Weighted-Average Grant Price [Roll Forward]
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 22.44
Granted (in dollars per share) | $ / shares	29.61
Vested (in dollars per share) | $ / shares	20.60
Forfeited (in dollars per share) | $ / shares	25.10
Outstanding, end of period (in dollars per share) | $ / shares	$ 26.85	$ 22.44
Aggregate intrinsic value [Abstract]
Outstanding, beginning of period | $	$ 25,251,904
Outstanding, end of period | $	$ 35,840,796	$ 25,251,904
2004 Plan [Member] | Stock Options [Member]
Options outstanding [Roll Forward]
Outstanding, beginning of period (in shares)	43,156
Granted (in shares)	0
Exercised (in shares)	(13,457)
Forfeited (in shares)	0
Outstanding, end of period (in shares)	29,699	43,156
Exercisable, end of period (in shares)	29,699
Options expected to vest, end of period (in shares)	0
Weighted-Average Exercise Price [Roll Forward]
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 10.28
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	10.28
Forfeited (in dollars per share) | $ / shares	0
Outstanding, end of period (in dollars per share) | $ / shares	10.28	$ 10.28
Exercisable, end of period (in dollars per share) | $ / shares	10.28
Options expected to vest, end of period (in dollars per share) | $ / shares	$ 0
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Threshold limit for common stock ownership to be ineligible to participate in ESPP	5.00%
Common stock authorized for issuance under the plan (in shares)	1,000,000
Number of plan periods | Plan	2
Discount from market price	15.00%
Maximum number of shares that may be granted per year to a single participant (in shares)	800
Employee Stock Purchase Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee subscription rate	1.00%
Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee subscription rate	10.00%
Cost of Product Sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense | $	$ 1,183,000	$ 1,145,000	575,000
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense | $	3,112,000	3,606,000	3,283,000
Selling, General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense | $	$ 11,553,000	$ 8,078,000	$ 7,380,000