Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, authorized shares (in shares)	900,000,000	900,000,000
Common stock, issued shares	43,784,939	84,048,081
Common stock, outstanding shares	43,784,939	84,048,081
Series A Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	36,000,000	36,000,000
Preferred stock, shares issued	1,225,734	61,435
Preferred stock, shares outstanding	1,224,712	61,435
Preferred stock, liquidation preference per share (in usd per share)	$ 25.00	$ 25.00
Series A Cumulative Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	36,000,000	36,000,000
Preferred stock, shares issued	61,435	0
Preferred stock, shares outstanding	60,592	0
Preferred stock, liquidation preference per share (in usd per share)	$ 25.00	$ 25.00
Series L Preferred Stock
Preferred stock, par value (in usd per share)	$ 0.001	$ 0
Preferred stock, shares authorized	9,000,000	0
Preferred stock, shares issued	8,080,740	0
Preferred stock, shares outstanding	8,080,740	0
Preferred stock, liquidation preference per share (in usd per share)	$ 28.37	$ 0