Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statement Of Operations) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Income Statements, Captions [Line Items]
Total revenues	$ 263,973,000	$ 166,483,000	$ 489,253,000	$ 317,838,000
Total costs and expenses	228,181,000	110,177,000	425,650,000	221,511,000
Income (loss) before income taxes	35,792,000	56,306,000	63,603,000	96,327,000
Income tax (expense) benefit	(483,000)	0	(802,000)	0
Equity (deficit) in income of subsidiaries	0	0	0	0
Net Income (loss)	35,309,000	56,306,000	62,801,000	96,327,000
Dividends on preferred stock	(4,474,000)	0	(9,337,000)	0
Accretion on preferred stock	(740,000)	0	(1,493,000)	0
Loss on redemption of preferred stock	0	0	(7,133,000)	0
Net Income Attributable to Common Shareholders	30,095,000	56,306,000	44,838,000	96,327,000
Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Total revenues	0	0	0	0
Total costs and expenses	(23,000)	31,000	(32,000)	41,000
Income (loss) before income taxes	23,000	(31,000)	32,000	(41,000)
Income tax (expense) benefit	0	0	0	0
Equity (deficit) in income of subsidiaries	(141,602,000)	(63,894,000)	(256,430,000)	(122,711,000)
Net Income (loss)	(141,579,000)	(63,925,000)	(256,398,000)	(122,752,000)
Dividends on preferred stock	0	0	0	0
Accretion on preferred stock	0	0	0	0
Loss on redemption of preferred stock	0	0	0	0
Net Income Attributable to Common Shareholders	(141,579,000)	(63,925,000)	(256,398,000)	(122,752,000)
Parent Company [Member] | Reportable Legal Entities [Member]
Condensed Income Statements, Captions [Line Items]
Total revenues	19,000	174,000	39,000	256,000
Total costs and expenses	106,335,000	7,731,000	193,700,000	26,599,000
Income (loss) before income taxes	(106,316,000)	(7,557,000)	(193,661,000)	(26,343,000)
Income tax (expense) benefit	0	0	0	0
Equity (deficit) in income of subsidiaries	141,602,000	63,894,000	256,430,000	122,711,000
Net Income (loss)	35,286,000	56,337,000	62,769,000	96,368,000
Dividends on preferred stock	4,474,000	0	9,337,000	0
Accretion on preferred stock	(740,000)	0	(1,493,000)	0
Loss on redemption of preferred stock	0	0	(7,133,000)	0
Net Income Attributable to Common Shareholders	30,072,000	56,337,000	44,806,000	96,368,000
Combined Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Income Statements, Captions [Line Items]
Total revenues	263,954,000	166,309,000	489,214,000	317,582,000
Total costs and expenses	121,869,000	102,415,000	231,982,000	194,871,000
Income (loss) before income taxes	142,085,000	63,894,000	257,232,000	122,711,000
Income tax (expense) benefit	(483,000)	0	(802,000)	0
Equity (deficit) in income of subsidiaries	0	0	0	0
Net Income (loss)	141,602,000	63,894,000	256,430,000	122,711,000
Dividends on preferred stock	0	0	0	0
Accretion on preferred stock	0	0	0	0
Loss on redemption of preferred stock	0	0	0	0
Net Income Attributable to Common Shareholders	141,602,000	63,894,000	256,430,000	122,711,000
Combined Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Condensed Income Statements, Captions [Line Items]
Total revenues	0	0	0	0
Total costs and expenses	0	0	0	0
Income (loss) before income taxes	0	0	0	0
Income tax (expense) benefit	0	0	0	0
Equity (deficit) in income of subsidiaries	0	0	0	0
Net Income (loss)	0	0	0	0
Dividends on preferred stock	0	0	0	0
Accretion on preferred stock	0	0	0	0
Loss on redemption of preferred stock	0	0	0	0
Net Income Attributable to Common Shareholders	$ 0	$ 0	$ 0	$ 0