Income Taxes - Tax Credit Carryforward Narrative (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Income Tax Contingency [Line Items]  
Tax credit carryforward, term 20 years
Internal Revenue Service (IRS)
 
Income Tax Contingency [Line Items]  
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation $ 13.9
State jurisdiction
 
Income Tax Contingency [Line Items]  
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation 13.1
Research and development | Internal Revenue Service (IRS)
 
Income Tax Contingency [Line Items]  
Tax credit carryforward 6.4
Tax credit carryforward, expiration date Dec. 31, 2025
Research and development | State jurisdiction
 
Income Tax Contingency [Line Items]  
Tax credit carryforward $ 6.9