Stockholders' Equity - Preferred Stock (Details) - shares	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Shares
Beginning balance (in shares)	14,369,965	14,370,060	14,370,060
Ending balance (in shares)	0		14,369,965	14,370,060
Weighted Avg. Dividend Rate
Balance	0.00%	6.50%	6.50%	6.50%
Shares converted	6.50%	6.50%
Number of shares converted into common stock (in shares)	0.8857
Common Stock
Shares
Shares converted (in shares)	(14,369,965)	(95)