Long-Term Debt (Tables)

6 Months Ended

Jun. 30, 2013

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

Long-term debt consists of the following:

	June 30, 2013			December 31, 2012
	(in thousands)
Senior notes:
3.25% Convertible senior notes due 2016:
Principal amount	$	115,000		$	115,000
Unamortized discount	(11,873		)	(13,671		)
3.25% Convertible senior notes due 2016, net of discount	103,127			101,329
7.75% Senior notes due 2022	500,000			500,000
Total senior notes	603,127			601,329
Credit facilities:
Corporate	—			49,000
PDCM	36,000			26,250
Total credit facilities	36,000			75,250
Total long-term debt	$	639,127		$	676,579