CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Thousands		Total	Series B Preferred Stock	Common Class A	Preferred Stock Series B Preferred Stock	Common Stock Common Class A	Common Stock Common Class B	Additional Paid-in Capital	Additional Paid-in Capital Common Class A	Accumulated Deficit
Balances at Dec. 31, 2016		$ 358,813				$ 236		$ 1,910,284		$ (1,551,707)
Balances (in shares) at Dec. 31, 2016						23,607,111	20,256
Net Income (loss)		17,435								17,435
Conversion of Class B common stock to Class A common stock (in shares)						20,256	(20,256)
Issuance of stock			$ 7,108	$ 61,213	$ 7,108	$ 45			$ 61,168
Issuance of stock (in shares)					303,291	4,472,083
Issuance of Class A common stock under stock-based compensation plans (in shares)						74,000
Repurchase of Class A common stock under stock-based compensation plans		(437)						(437)
Repurchase of Class A common stock under stock-based compensation plans (in shares)						(32,729)
Stock-based compensation		3,926						3,926
Dividends declared	[1]	(61,741)								(61,741)
Balances at Dec. 31, 2017		386,317			$ 7,108	$ 281		1,974,941		(1,596,013)
Balances (in shares) at Dec. 31, 2017					303,291	28,140,721
Net Income (loss)		(65,492)								(65,492)
Issuance of stock			$ 1,030	$ 21,065	$ 1,030	$ 21			$ 21,044
Issuance of stock (in shares)					42,865	2,074,205
Issuance of Class A common stock under stock-based compensation plans		124				$ 1		123
Issuance of Class A common stock under stock-based compensation plans (in shares)						164,585
Cumulative-effect of accounting change (see Note 2) | ASU No. 2016-01		4,059								4,059
Repurchase of Class A common stock under stock-based compensation plans		(327)						(327)
Repurchase of Class A common stock under stock-based compensation plans (in shares)						(33,865)
Stock-based compensation		1,500						1,500
Dividends declared	[1]	(37,586)								(37,586)
Balances at Sep. 30, 2018		$ 310,690			$ 8,138	$ 303		$ 1,997,281		$ (1,695,032)
Balances (in shares) at Sep. 30, 2018					346,156	30,345,646

[1] The Board of Directors approved and the Company declared and paid dividends of $2.275 and $1.30 per common share for the year ended December 31, 2017 and the nine months ended September 30, 2018, respectively. The Board of Directors approved and the Company declared and paid dividends of $1.113 and $1.3125 per preferred share for the year ended December 31, 2017 and the nine months ended September 30, 2018, respectively.