Senior Notes (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
	Oct. 17, 2016	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Exchange Offers on Senior Notes
Aggregate Principal amount	$ 400,000
Principal		$ 408,868		$ 346,774	$ 408,868
Exchanges				0	290,366	$ 0
Cash Paid on tender of 2019 and 2024 senior notes	26,000			0	18,335	0
Accrued Interest Paid	7,700
Debt restructuring costs	4,700	200	$ 4,500	$ 23	4,665	0
Senior 8.50 Percent Notes Due 2019
Exchange Offers on Senior Notes
Aggregate Principal amount	$ 237,900
Principal		$ 62,094			$ 62,094	300,000
Interest rate (as a percent)	8.50%	8.50%		8.50%	8.50%
Aggregate Principal Remaining	$ 62,100
Senior 12.0 Percent Notes Due 2021
Exchange Offers on Senior Notes
Principal		$ 290,366		$ 290,366	$ 290,366
Interest rate (as a percent)	12.00%	12.00%		12.00%	12.00%
Exchanges	$ 290,400
Interest rate (as a percent) Effective	6.46%
Senior 6.375 Percent Notes Due 2024
Exchange Offers on Senior Notes
Aggregate Principal amount	$ 143,600
Principal		$ 56,408		$ 56,408	$ 56,408	$ 200,000
Interest rate (as a percent)	6.375%	6.375%		6.375%	6.375%
Aggregate Principal Remaining	$ 56,400