Senior Notes (Details 1) - USD ($) $ in Thousands, shares in Millions			3 Months Ended	12 Months Ended
	Mar. 31, 2017	Feb. 28, 2017	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 17, 2016
Equity Offering [Line Items]
Common Stock Shares Issued		13.5
Net proceeds of common stock issued		$ 64,700
Write-off of deferred financing costs and original issue discount			$ 700	$ 702	$ 1,254	$ 0
Debt Instrument [Line Items]
Principal				346,774	408,868
Unamortized discount and debt issuance costs				14,475	19,220
Unamortized Deferred Gain Forgiven Debt				(72,967)	(85,362)
Carrying Value				405,266	475,009
Fair Value				$ 361,746	406,545
Senior 8.50 Percent Notes Due 2019
Equity Offering [Line Items]
Redemption price percentage of principal amount	101.417%
Interest paid	$ 1,500
Principal amount with premium of notes redeemed	63,000		$ 63,000
Total Redemption costs	64,500
Write-off of deferred financing costs and original issue discount	$ 700
Debt Instrument [Line Items]
Principal					62,094	300,000
Unamortized discount and debt issuance costs					711
Carrying Value					61,383
Fair Value					$ 57,903
Interest rate (as a percent)				8.50%	8.50%		8.50%
Senior 6.375 Percent Notes Due 2024
Debt Instrument [Line Items]
Principal				$ 56,408	$ 56,408	$ 200,000
Unamortized discount and debt issuance costs				861	998
Unamortized Deferred Gain Forgiven Debt				0
Carrying Value				55,547	55,410
Fair Value				$ 45,973	$ 42,306
Interest rate (as a percent)				6.375%	6.375%		6.375%
Senior 12.0 Percent Notes Due 2021
Debt Instrument [Line Items]
Principal				$ 290,366	$ 290,366
Unamortized discount and debt issuance costs				13,614	17,511
Unamortized Deferred Gain Forgiven Debt				(72,967)	(85,362)
Carrying Value				349,719	358,217
Fair Value				$ 315,773	$ 306,336
Interest rate (as a percent)				12.00%	12.00%		12.00%