Income Taxes (Narrative) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
Income Tax Examination [Line Items] | |||
Valuation allowance increases | $ 92.7 | $ 7.9 | $ 88.8 |
Tax benefit of stock option | 57.0 | ||
Federal [Member] | |||
Income Tax Examination [Line Items] | |||
Net operating loss carryforwards | 1,424.0 | ||
Research and development tax credits | 75.0 | ||
State and Local Jurisdiction [Member] | |||
Income Tax Examination [Line Items] | |||
Net operating loss carryforwards | 494.0 | ||
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member] | |||
Income Tax Examination [Line Items] | |||
Research and development tax credits | $ 25.0 |