Guarantor/Non-Guarantor Condensed Consolidated Financial Statements - Balance Sheet (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 6,291	$ 86,197	$ 21,857	$ 22,011
Receivables, net of allowance	173,535	145,234
Intercompany receivable (payable)	0	0
Deferred income taxes	16,109	15,433
Inventory	12,177	11,184
Prepaid expenses and other current assets	10,019	11,564
Total current assets	218,131	269,612
Net property and equipment	982,724	793,956
Investments in subsidiaries	0	0
Intangible assets, net of amortization	46,020	52,680
Goodwill	41,683	41,683
Noncurrent deferred income taxes	373	735
Other long-term assets	14,253	14,088
Total assets	1,303,184	1,172,754	946,888
Current liabilities:
Accounts payable	84,919	66,440
Current portion of long-term debt	872	872
Prepaid drilling contracts	2,880	3,966
Accrued expenses	58,961	68,402
Total current liabilities	147,632	139,680
Long-term debt, less current portion	498,502	418,728
Noncurrent deferred income taxes	107,727	94,745
Other long-term liabilities	6,988	9,156
Total liabilities	760,849	662,309
Total shareholders' equity	542,335	510,445
Total liabilities and shareholders' equity	1,303,184	1,172,754
Parent [Member]
Current assets:
Cash and cash equivalents	8,663	91,932	21,272	15,737
Receivables, net of allowance	6	(2)
Intercompany receivable (payable)	(125,111)	(122,552)
Deferred income taxes	751	1,408
Inventory	0	0
Prepaid expenses and other current assets	1,403	285
Total current assets	(114,288)	(28,929)
Net property and equipment	2,502	1,605
Investments in subsidiaries	1,099,973	932,237
Intangible assets, net of amortization	66	171
Goodwill	0	0
Noncurrent deferred income taxes	47,649	30,835
Other long-term assets	10,114	11,949
Total assets	1,046,016	947,868
Current liabilities:
Accounts payable	761	1,090
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	3,630	16,779
Total current liabilities	4,391	17,869
Long-term debt, less current portion	498,389	417,747
Noncurrent deferred income taxes	0	921
Other long-term liabilities	151	137
Total liabilities	502,931	436,674
Total shareholders' equity	543,085	511,194
Total liabilities and shareholders' equity	1,046,016	947,868
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(3,648)	(13,879)	(4,468)	(1,840)
Receivables, net of allowance	132,086	112,531
Intercompany receivable (payable)	143,717	131,585
Deferred income taxes	7,245	8,644
Inventory	5,265	4,533
Prepaid expenses and other current assets	6,490	6,304
Total current assets	291,155	249,718
Net property and equipment	846,828	675,679
Investments in subsidiaries	223,520	221,201
Intangible assets, net of amortization	15,636	18,829
Goodwill	0	0
Noncurrent deferred income taxes	0	0
Other long-term assets	1,423	2,124
Total assets	1,378,562	1,167,551
Current liabilities:
Accounts payable	70,738	57,150
Current portion of long-term debt	850	850
Prepaid drilling contracts	2,207	1,297
Accrued expenses	45,728	45,012
Total current liabilities	119,523	104,309
Long-term debt, less current portion	0	850
Noncurrent deferred income taxes	154,351	124,659
Other long-term liabilities	4,715	5,496
Total liabilities	278,589	235,314
Total shareholders' equity	1,099,973	932,237
Total liabilities and shareholders' equity	1,378,562	1,167,551
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	1,276	8,144	5,053	8,114
Receivables, net of allowance	44,976	32,724
Intercompany receivable (payable)	(18,606)	(9,033)
Deferred income taxes	8,113	5,381
Inventory	6,912	6,651
Prepaid expenses and other current assets	2,126	4,975
Total current assets	44,797	48,842
Net property and equipment	134,144	117,422
Investments in subsidiaries	0	0
Intangible assets, net of amortization	30,318	33,680
Goodwill	41,683	41,683
Noncurrent deferred income taxes	373	735
Other long-term assets	2,716	15
Total assets	254,031	242,377
Current liabilities:
Accounts payable	13,420	8,200
Current portion of long-term debt	22	22
Prepaid drilling contracts	673	2,669
Accrued expenses	13,136	6,631
Total current liabilities	27,251	17,522
Long-term debt, less current portion	113	131
Noncurrent deferred income taxes	1,025	0
Other long-term liabilities	2,122	3,523
Total liabilities	30,511	21,176
Total shareholders' equity	223,520	221,201
Total liabilities and shareholders' equity	254,031	242,377
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables, net of allowance	(3,533)	(19)
Intercompany receivable (payable)	0	0
Deferred income taxes	0	0
Inventory	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(3,533)	(19)
Net property and equipment	(750)	(750)
Investments in subsidiaries	(1,323,493)	(1,153,438)
Intangible assets, net of amortization	0	0
Goodwill	0	0
Noncurrent deferred income taxes	(47,649)	(30,835)
Other long-term assets	0	0
Total assets	(1,375,425)	(1,185,042)
Current liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	(3,533)	(20)
Total current liabilities	(3,533)	(20)
Long-term debt, less current portion	0	0
Noncurrent deferred income taxes	(47,649)	(30,835)
Other long-term liabilities	0	0
Total liabilities	(51,182)	(30,855)
Total shareholders' equity	(1,324,243)	(1,154,187)
Total liabilities and shareholders' equity	$ (1,375,425)	$ (1,185,042)