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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

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Long-Term Debt - Narrative (Details)								1 Months Ended	12 Months Ended
Long-Term Debt - Narrative (Details)	Nov. 21, 2017	May 04, 2017 USD ($) bank	Dec. 21, 2016 USD ($)	Dec. 13, 2016 USD ($)	Dec. 12, 2016	Oct. 14, 2016 USD ($)	Oct. 06, 2016 USD ($)	Jan. 31, 2016	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 11, 2017 USD ($)	Sep. 30, 2017 USD ($)	Mar. 29, 2017 USD ($)	Oct. 31, 2016 USD ($)	Feb. 19, 2016 USD ($)	Feb. 18, 2016 USD ($)	Jun. 04, 2015 USD ($)	Apr. 21, 2015 USD ($)	Aug. 18, 2014 USD ($)	Dec. 21, 2012 USD ($)	Oct. 17, 2012 USD ($)	Mar. 31, 2011 USD ($)
Debt Instrument [Line Items]
Long-tern debt									$ 2,073,724,000
Deferred finance costs									34,781,000	$ 27,174,000
Capitalized interest costs									9,470,000	9,148,000	$ 13,580,000
Revolving credit agreement
Debt Instrument [Line Items]
Debt issued									0	0
Building loans
Debt Instrument [Line Items]
Stated interest rate																							4.00%
Long-tern debt																							$ 2,400,000
Monthly interest and principal payments									20,000
Debt issued									0	0
Capitalized interest costs										400,000
Senior notes
Debt Instrument [Line Items]
Write off of remaining premium and discount									10,800,000
Construction loans
Debt Instrument [Line Items]
Debt issued									23,724,000	21,049,000
Oil and gas properties
Debt Instrument [Line Items]
Capitalized interest costs									$ 9,500,000	$ 8,700,000
Nova Scotia, Amegy, KeyBank \| Base Rate \| Minimum
Debt Instrument [Line Items]
Stated interest rate									0.50%
Nova Scotia, Amegy, KeyBank \| Base Rate \| Maximum
Debt Instrument [Line Items]
Stated interest rate									1.50%
Nova Scotia, Amegy, KeyBank \| Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate									0.50%
Nova Scotia, Amegy, KeyBank \| Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate									1.00%
Nova Scotia, Amegy, KeyBank \| Eurodollar \| Minimum
Debt Instrument [Line Items]
Stated interest rate									1.50%
Nova Scotia, Amegy, KeyBank \| Eurodollar \| Maximum
Debt Instrument [Line Items]
Stated interest rate									2.50%
InterBank \| Revolving credit agreement \| Construction loans
Debt Instrument [Line Items]
Maximum borrowing capacity																		$ 24,500,000
Stated interest rate																		4.50%
InterBank \| Letter of credit \| Construction loans
Debt Instrument [Line Items]
Required minimum down payment percentage								30.00%
Deferred finance costs									$ 100,000
Debt issued									$ 23,700,000
Amended and Restated Credit Agreement \| Maximum
Debt Instrument [Line Items]
Debt covenant ratio for future EBITDAX									4.00
Amended and Restated Credit Agreement \| Revolving credit agreement
Debt Instrument [Line Items]
Debt covenant ratio for EBITDAX									3.00
Amended and Restated Credit Agreement \| Nova Scotia, Amegy, KeyBank \| Revolving credit agreement
Debt Instrument [Line Items]
Maximum borrowing capacity									$ 1,500,000,000
Required minimum down payment percentage				85.00%	80.00%
Amended and Restated Credit Agreement \| Nova Scotia, Amegy, KeyBank \| Revolving credit agreement \| Minimum
Debt Instrument [Line Items]
Borrowing base																$ 700,000,000
Amended and Restated Credit Agreement \| Nova Scotia, Amegy, KeyBank \| Unsecured Debt \| Revolving credit agreement
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 1,600,000,000												1,400,000,000	$ 1,200,000,000
Long-term line of credit outstanding																$ 950,000,000
Basis spread on variable rate				0.50%
Amended and Restated Credit Agreement \| Nova Scotia, Amegy, KeyBank \| Revolving credit agreement
Debt Instrument [Line Items]
Borrowing base		$ 700,000,000.0							1,200,000,000.0				$ 1,000,000,000.0
Minimum acquisition payment limit														$ 50,000,000.0
Minimum disposition of property limit														$ 50,000,000.0
Number of banks added to syndicate \| bank		5
Increase (decrease) in interest rate	0.50%
Amended and Restated Credit Agreement \| Nova Scotia, Amegy, KeyBank \| Letter of credit
Debt Instrument [Line Items]
Long-term line of credit outstanding									241,000,000
Line of credit facility, elected commitment									1,000,000,000.0
Future borrowings available									759,000,000
Disposition costs, maximum expenses allowed									$ 3,000,000.0
7.75% Senior Notes Due 2020 \| Senior notes
Debt Instrument [Line Items]
Stated interest rate									7.75%	7.75%
Aggregate principal amount																				$ 600,000,000.0
Conversion ratio for cash consideration							1.042
Debt repurchase, amount tendered							$ 403,500,000
Repurchased face amount						$ 196,500,000									$ 600,000,000.0
Redemption price percentage redeemed						103.875%
Debt issued									$ 0	$ 0
6.625% Senior Notes Due 2023 \| Senior notes
Debt Instrument [Line Items]
Stated interest rate									6.625%	6.625%									6.625%
Long-tern debt																			$ 343,600,000
Aggregate principal amount																			$ 350,000,000.0
Deferred finance costs									$ 5,200,000
Debt issued									$ 350,000,000	$ 350,000,000
6.000% Senior Notes Due 2024 \| Senior notes
Debt Instrument [Line Items]
Stated interest rate						6.00%			6.00%	6.00%
Aggregate principal amount						$ 650,000,000.0
Proceeds from issuance of Senior notes						$ 638,900,000
Deferred finance costs									$ 9,900,000
Debt issued									$ 650,000,000	$ 650,000,000
6.375% Senior Notes Due 2025 \| Senior notes
Debt Instrument [Line Items]
Stated interest rate			6.375%						6.375%	6.375%
Aggregate principal amount			$ 600,000,000
Proceeds from issuance of Senior notes			$ 584,700,000
Deferred finance costs									$ 14,000,000
Debt issued									$ 600,000,000	$ 600,000,000
6.375% Senior Notes Due 2026 \| Senior notes
Debt Instrument [Line Items]
Stated interest rate									6.375%			6.375%
Long-tern debt												$ 444,300,000
Aggregate principal amount												$ 450,000,000
Deferred finance costs									$ 5,500,000
Debt issued									$ 450,000,000	$ 0
October Notes \| Senior notes
Debt Instrument [Line Items]
Discount issue price, percent																						98.534%
Unamortized discount																						$ 3,700,000
Effective interest rate																						8.00%
October Notes \| Wells Fargo Bank \| Senior notes
Debt Instrument [Line Items]
Stated interest rate																						7.75%
Aggregate principal amount																						$ 250,000,000
December Notes \| Senior notes
Debt Instrument [Line Items]
Effective interest rate																					7.531%
Premium issue price, percent																					101.00%
Unamortized premium																					$ 500,000
December Notes \| Wells Fargo Bank \| Senior notes
Debt Instrument [Line Items]
Stated interest rate																				7.75%	7.75%
Aggregate principal amount																					$ 50,000,000
August Notes \| Senior notes
Debt Instrument [Line Items]
Effective interest rate																				6.561%
Premium issue price, percent																				106.00%
Unamortized premium																				$ 18,000,000
August Notes \| Wells Fargo Bank \| Senior notes
Debt Instrument [Line Items]
Aggregate principal amount																				$ 300,000,000