Indebtedness (Schedule of Indebtedness) (Details) - USD ($) $ in Thousands	Jun. 03, 2014	Jun. 30, 2015		Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014
Total indebtedness		$ 692,823		$ 1,021,031	$ 1,020,462	$ 1,023,033	$ 1,025,566
Less: current maturities		(3,364)		(3,176)
Long-term debt, less current maturities of long-term debt		1,014,459		1,017,855	1,020,462	$ 1,023,033	$ 1,025,566
Long-term debt, less current maturities		689,459					1,025,566
Intercompany promissory note		325,000
Noncurrent portion of indebtedness including promissory note		1,014,459					1,025,566
8.25% Notes [Member]
Total indebtedness		539,459	[1]	542,855	545,462	548,033	550,566	[1]
Long-term debt, less current maturities of long-term debt		539,459		542,855	545,462	548,033	550,566
Noncurrent portion of indebtedness including promissory note							550,566
Senior notes, stated percentage	8.25%
Maturity date	Feb. 15, 2018
Intercompany Promissory Note [Member]
Total indebtedness				325,000
Long-term debt, less current maturities of long-term debt		325,000		325,000
Derivative Instruments Premium Financing [Member]
Total indebtedness		3,364		3,176
Revolving Credit Sub-Facility [Member]
Total indebtedness		150,000		150,000	475,000	475,000	475,000
Long-term debt, less current maturities of long-term debt		$ 150,000		$ 150,000	$ 475,000	$ 475,000	475,000
Noncurrent portion of indebtedness including promissory note							$ 475,000

[1] Includes unamortized premium on the 8.25% Senior Notes.