Fair Value Measurements (Schedule of Carrying Value and Estimated Fair Value of Debt Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Apr. 14, 2015	Dec. 31, 2014
8.625% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	$ 0	$ 600,000	$ 600,000
8.625% Senior Notes [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	0		596,555
8.625% Senior Notes [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	0		597,000
Seven Point Five Percent Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	600,000		600,000
Seven Point Five Percent Senior Notes [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	601,360		601,466
Seven Point Five Percent Senior Notes [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	630,000		573,000
6.25% Senior Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	650,000		0
6.25% Senior Notes [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	650,000		0
6.25% Senior Notes [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	648,375		0
Other Long Term Debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	4,425		4,425
Other Long Term Debt [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	4,425		4,425
Other Long Term Debt [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	4,204		4,071
Deferred Purchase Payment [Member] | Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	0		148,900
Deferred Purchase Payment [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long term debt	$ 0		$ 148,558