Fair Value Measurements (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents		$ 16,121	$ 269	$ 85,663
Restricted cash		181	429	173
Commodity derivatives, net	[1]	9,726	25,885	(126,689)
Convertible preferred securities	[2]	12,800	13,300	15,000
Other assets and liabilities	[3]	7,154	8,203	9,035
Total		45,982	48,086	(16,818)
Level 1
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents		16,121	269	85,663
Restricted cash		181	429	173
Commodity derivatives, net	[1]	34,337	72,868	32,606
Convertible preferred securities	[2]	0	0	0
Other assets and liabilities	[3]	10,814	10,869	10,671
Total		61,453	84,435	129,113
Level 2
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents		0	0	0
Restricted cash		0	0	0
Commodity derivatives, net	[1]	(24,611)	(46,983)	(159,295)
Convertible preferred securities	[2]	0	0	0
Other assets and liabilities	[3]	(4,010)	(2,666)	(1,636)
Total		(28,621)	(49,649)	(160,931)
Level 3
Assets and liabilities measured at fair value on a recurring basis
Cash equivalents		0	0	0
Restricted cash		0	0	0
Commodity derivatives, net	[1]	0	0	0
Convertible preferred securities	[2]	12,800	13,300	15,000
Other assets and liabilities	[3]	350	0	0
Total		$ 13,150	$ 13,300	$ 15,000

[1] Includes associated cash posted/received as collateral

[2] Recorded in “Other noncurrent assets” on the Company’s Condensed Consolidated Balance Sheets

[3] Included in other assets and liabilities are deferred compensation assets (Level 1), interest rate derivatives (Level 2), and contingent consideration to the former owners of Kay Flo Industries, Inc (Level 3).