Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 2,906,000	$ 0
Additions based on tax positions related to prior years	0	2,906,000
Balance at December 31	$ 2,906,000	$ 2,906,000