Debt (Details) - USD ($) $ in Thousands			6 Months Ended	12 Months Ended
	Jul. 15, 2015	Dec. 16, 2014	Dec. 31, 2015	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Debt
Unamortized discount expensed as reorganization item				$ 378,705
Liabilities Subject to Compromise
Debt
Accrued interest	$ 74,200
2017 Senior Notes
Debt
Unsecured notes outstanding			$ 350,000	$ 350,000
Interest rate (as a percent)			9.75%	9.75%
Unamortized discount						$ 1,400
Discount amortization expense				$ 300
Unamortized discount expensed as reorganization item	1,100
Effective interest rate (as a percent)				5.57%
Interest expense			$ 0
2017 Senior Notes | Liabilities Subject to Compromise
Debt
Accrued interest	14,100
2019 Senior Notes
Debt
Interest rate (as a percent)		7.25%			7.25%
Unamortized discount		$ 287,500				284,900
Discount amortization expense				$ 34,400
Unamortized discount expensed as reorganization item	250,400
Effective interest rate (as a percent)				9.86%
Debt assumed		$ 577,900
Interest expense			0
2019 Senior Notes | Liabilities Subject to Compromise
Debt
Accrued interest	24,300
2020 Senior Notes
Debt
Interest rate (as a percent)		7.50%			7.50%
Unamortized discount		$ 117,700				$ 116,900
Discount amortization expense				$ 11,000
Unamortized discount expensed as reorganization item	105,800
Effective interest rate (as a percent)				9.01%
Debt assumed		$ 222,100
Interest expense			$ 0
2020 Senior Notes | Liabilities Subject to Compromise
Debt
Accrued interest	$ 5,500