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Stockholders' equity (Share-based compensation) (Details) | 3 Months Ended
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Mar. 31, 2016 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Number of options granted (in shares) | 818,620
Granted stock options, exercise price (in dollars per share) | $ / shares | $ 9.39
Restricted Stock and Restricted Stock Units |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Number of equity instruments other than options granted (in shares) | 1,670,270
Restricted Stock and Restricted Stock Units | Board of Directors |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Number of equity instruments other than options granted (in shares) | 119,817
Award vesting period | 12 months
Restricted Stock and Restricted Stock Units with Specified Vesting Period |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Number of equity instruments other than options granted (in shares) | 1,292,553
Award vesting period | 4 years
Performance Shares |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Number of equity instruments other than options granted (in shares) | 257,900
Performance Shares | Share-based Compensation Award, Tranche One |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Performance measurement period | 1 year
Performance Shares | Share-based Compensation Award, Tranche Two |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Performance measurement period | 2 years
Performance Shares | Share-based Compensation Award, Tranche Three |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Performance measurement period | 3 years
Performance Shares | Minimum |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Share conversion ratio | 0
Performance Shares | Maximum |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Share conversion ratio | 2

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- Definition Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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