Income Taxes - Additional disclosure and 2017 Tax Act (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Income Taxes
Additional income tax benefit from effect of Tax Cuts and Jobs Act of 2017	$ 1.7
2017 Tax Act, Amount of increase in gross deferred tax assets	6.8
2017 Tax Act, Increase in deferred tax assets valuation allowance	$ 6.8