Stockholders' Equity and Employee Stock Option Plans Stock option outstanding by exercise price range (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	7 years 6 months 15 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Options and SARS, Outstanding, Weighted Average Exercise Price	$ 24.72	$ 34.00	$ 41.30		$ 60.80
Options and SARS, Outstanding, Number	285,536	259,679	410,484	550,540	393,931
Options, Vested and Expected to Vest, Outstanding, Number	273,003
Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	7 years 6 months 11 days
Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 25.10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 0
Options, Exercisable, Number	112,091
Options, Exercisable, Weighted Average Remaining Contractual Term	5 years 7 months 13 days
Options, Exercisable, Weighted Average Exercise Price	$ 39.15
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 0
Exercise Price Range $6.90 - $9.10 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 6.90
Exercise Price Range, Upper Range Limit	$ 9.10
Exercise Price Range, Number of Outstanding Options and SARS	6,500
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	9 years 5 months 5 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 8.25
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $9.11 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 9.11
Exercise Price Range, Upper Range Limit	$ 9.11
Exercise Price Range, Number of Outstanding Options and SARS	89,000
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	9 years 5 months 12 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 9.11
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $9.15 - $22.30 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 9.15
Exercise Price Range, Upper Range Limit	$ 22.30
Exercise Price Range, Number of Outstanding Options and SARS	24,400
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	8 years 8 months 7 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 15.46
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $22.4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 22.40
Exercise Price Range, Upper Range Limit	$ 22.40
Exercise Price Range, Number of Outstanding Options and SARS	44,000
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	8 years 3 months
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 22.40
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $23.70 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 23.70
Exercise Price Range, Upper Range Limit	$ 23.70
Exercise Price Range, Number of Outstanding Options and SARS	35,960
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	7 years 5 months 8 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 23.70
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $24.20 - $26.50 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 24.20
Exercise Price Range, Upper Range Limit	$ 26.50
Exercise Price Range, Number of Outstanding Options and SARS	9,800
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	7 years 11 months 20 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 24.92
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $31.70 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 31.70
Exercise Price Range, Upper Range Limit	$ 31.70
Exercise Price Range, Number of Outstanding Options and SARS	34,476
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	6 years 2 months 5 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 31.70
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $32.50 - $35.20 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 32.50
Exercise Price Range, Upper Range Limit	$ 35.20
Exercise Price Range, Number of Outstanding Options and SARS	12,400
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	6 years
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 33.37
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $74.60 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 74.60
Exercise Price Range, Upper Range Limit	$ 90.80
Exercise Price Range, Number of Outstanding Options and SARS	25,000
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	1 year 7 months 17 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 74.60
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0
Exercise Price Range $90.80 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Price Range, Lower Range Limit	$ 90.80
Exercise Price Range, Upper Range Limit	$ 90.80
Exercise Price Range, Number of Outstanding Options and SARS	4,000
Options and SARS Outstanding, Weighted Average Remaining Contractual Term	4 months 20 days
Exercise Price Range, Outstanding Options, Weighted Average Exercise Price	$ 90.80
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 0