Income Taxes - Operating Loss Carryforwards (Details) $ in Millions	Dec. 31, 2015 USD ($)
Federal [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 104.3
Unrecognized tax benefits resulting from the exercise of employee stock awards	57.2
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	96.3
Unrecognized tax benefits resulting from the exercise of employee stock awards	22.9
Research Tax Credit Carryforward [Member] | Federal [Member]
Operating Loss Carryforwards [Line Items]
Credit carryforwards	4.2
Research Tax Credit Carryforward [Member] | State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	73.0
Credit carryforwards	$ 4.8