Stockholders' Equity - Bryanston Settlement Agreement (Details) - USD ($)		12 Months Ended
	Mar. 07, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Interest expense		$ 19,269,000	$ 524,000	$ 2,643,000
Series E
Class of Stock [Line Items]
Payments for Repurchase of Private Placement	$ 30,700,000
Redemption of preferred stock	$ 1,500,000
Mandatorily Redeemable Preferred Stock | Series E
Class of Stock [Line Items]
Interest expense			$ 231,000	$ 1,200,000