Income Taxes - Net Operating Loss Carry Forward (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Market capitalization used in net operating loss analysis		$ 124.5
Annual limitation on usage of net operating losses	$ 3.0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		$ 210.3