Income Taxes - Summary of open tax years by major jurisdiction (Details)	12 Months Ended
	Dec. 31, 2014
United States | Minimum
Income Tax Contingency [Line Items]
Open tax year	2009
United States | Maximum
Income Tax Contingency [Line Items]
Open tax year	2014
United Kingdom | Minimum
Income Tax Contingency [Line Items]
Open tax year	2009
United Kingdom | Maximum
Income Tax Contingency [Line Items]
Open tax year	2014
Ireland | Minimum
Income Tax Contingency [Line Items]
Open tax year	2010
Ireland | Maximum
Income Tax Contingency [Line Items]
Open tax year	2014
Canada | Minimum
Income Tax Contingency [Line Items]
Open tax year	2010
Canada | Maximum
Income Tax Contingency [Line Items]
Open tax year	2014
Switzerland | Minimum
Income Tax Contingency [Line Items]
Open tax year	2011
Switzerland | Maximum
Income Tax Contingency [Line Items]
Open tax year	2014
Denmark | Minimum
Income Tax Contingency [Line Items]
Open tax year	2011
Denmark | Maximum
Income Tax Contingency [Line Items]
Open tax year	2014