Preferred Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 24, 2018	Dec. 31, 2017	Aug. 10, 2017
Preferred Stock Disclosure [Line Items]
Preferred Stock, Par Value								$ 250,000
Preferred Stock, Shares Issued	200,000			200,000			250,000	250,000
Preferred Stock, Dividend Rate, Percentage	8.875%
Preferred Stock, Par or Stated Value Per Share	$ 0.01			$ 0.01			$ 0.01	$ 0.01
Issuance of warrants to purchase Common Stock		2,750,000
Class of Warrant or Right, Term		10 years
Class of Warrant or Right, Exercise Price of Warrants or Rights								16.08
Cash purchase price per share of Preferred Stock								970.00
Sale of preferred stock, net of issuance costs		$ 236,404
Temporary Equity, Liquidation Preference Per Share								$ 1,000.00
Maximum Preferred Stock Shares Redeemable Within the First Year								50,000
Preferred Stock Shares Redeemed						50,000
Preferred Stock, Percentage Redeemed						20.00%
Payments for Repurchase of Redeemable Preferred Stock	$ 50,500
Loss on redemption of preferred stock	0		$ 0	$ 7,133	$ 0
Preferred Stock Redemption Costs				100
Preferred Stock Redemption Premium				7,000
Total Consideration for Repurchase of Preferred Stock				50,030
Redemption of Preferred Stock				$ (42,897)
Preferred Stock, Redemption Premium, Percentage				104.4375%
Preferred Stock, Percent of Ownership to be Able to Vote		50.00%
Preferred Stock, Prohibited Distributions		$ 15,000
Dividends on preferred stock	(4,474)			$ (9,337)	0
Accretion on preferred stock	$ (740)		$ 0	$ (1,493)	$ 0
On or before the seventh anniversary of the Preferred Stock Issuance Date [Domain]
Preferred Stock Disclosure [Line Items]
Preferred Stock, Dividend Rate, Percentage		12.00%
After August 10, 2024 [Domain]
Preferred Stock Disclosure [Line Items]
Preferred Stock, Dividend Rate, Percentage		12.00%
Libor Rate to Calculate Preferred Stock Dividend Rate		10.00%