Guarantor/Non-Guarantor Condensed Consolidated Financial Statements - Balance Sheet (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 21,401	$ 86,197	$ 15,311	$ 22,011
Receivables, net of allowance for doubtful accounts	163,643	145,234
Intercompany receivable (payable)	0	0
Deferred income taxes	16,259	15,433
Inventory	12,220	11,184
Prepaid expenses and other current assets	12,207	11,564
Total current assets	225,730	269,612
Net property and equipment	868,488	793,956
Investments in subsidiaries	0	0
Intangible assets, net of amortization	50,503	52,680
Goodwill	41,683	41,683
Noncurrent deferred income taxes	0	735
Other long-term assets	12,680	14,088
Total assets	1,199,084	1,172,754	847,987
Current liabilities:
Accounts payable	85,117	66,440
Current portion of long-term debt	873	872
Prepaid drilling contracts	4,733	3,966
Accrued expenses	53,465	68,402
Total current liabilities	144,188	139,680
Long-term debt, less current portion	418,279	418,728
Noncurrent deferred income taxes	100,701	94,745
Other long-term liabilities	9,375	9,156
Total liabilities	672,543	662,309
Total shareholders' equity	526,541	510,445
Total liabilities and shareholders' equity	1,199,084	1,172,754
Parent [Member]
Current assets:
Cash and cash equivalents	21,142	91,932	15,379	15,737
Receivables, net of allowance for doubtful accounts	2	(2)
Intercompany receivable (payable)	(126,574)	(122,552)
Deferred income taxes	553	1,408
Inventory	0	0
Prepaid expenses and other current assets	246	285
Total current assets	(104,631)	(28,929)
Net property and equipment	1,751	1,605
Investments in subsidiaries	1,004,501	932,237
Intangible assets, net of amortization	176	171
Goodwill	0	0
Noncurrent deferred income taxes	36,436	30,835
Other long-term assets	11,208	11,949
Total assets	949,441	947,868
Current liabilities:
Accounts payable	452	1,090
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	3,541	16,779
Total current liabilities	3,993	17,869
Long-term debt, less current portion	417,954	417,747
Noncurrent deferred income taxes	0	921
Other long-term liabilities	203	137
Total liabilities	422,150	436,674
Total shareholders' equity	527,291	511,194
Total liabilities and shareholders' equity	949,441	947,868
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(6,505)	(13,879)	(2,829)	(1,840)
Receivables, net of allowance for doubtful accounts	123,415	112,531
Intercompany receivable (payable)	142,819	131,585
Deferred income taxes	6,656	8,644
Inventory	4,971	4,533
Prepaid expenses and other current assets	7,890	6,304
Total current assets	279,246	249,718
Net property and equipment	743,910	675,679
Investments in subsidiaries	225,515	221,201
Intangible assets, net of amortization	17,768	18,829
Goodwill	0	0
Noncurrent deferred income taxes	0	0
Other long-term assets	1,457	2,124
Total assets	1,267,896	1,167,551
Current liabilities:
Accounts payable	76,081	57,150
Current portion of long-term debt	850	850
Prepaid drilling contracts	2,722	1,297
Accrued expenses	43,997	45,012
Total current liabilities	123,650	104,309
Long-term debt, less current portion	200	850
Noncurrent deferred income taxes	134,255	124,659
Other long-term liabilities	5,290	5,496
Total liabilities	263,395	235,314
Total shareholders' equity	1,004,501	932,237
Total liabilities and shareholders' equity	1,267,896	1,167,551
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	6,764	8,144	2,761	8,114
Receivables, net of allowance for doubtful accounts	43,844	32,724
Intercompany receivable (payable)	(16,245)	(9,033)
Deferred income taxes	9,050	5,381
Inventory	7,249	6,651
Prepaid expenses and other current assets	4,071	4,975
Total current assets	54,733	48,842
Net property and equipment	123,577	117,422
Investments in subsidiaries	0	0
Intangible assets, net of amortization	32,559	33,680
Goodwill	41,683	41,683
Noncurrent deferred income taxes	0	735
Other long-term assets	15	15
Total assets	252,567	242,377
Current liabilities:
Accounts payable	8,584	8,200
Current portion of long-term debt	23	22
Prepaid drilling contracts	2,011	2,669
Accrued expenses	9,545	6,631
Total current liabilities	20,163	17,522
Long-term debt, less current portion	125	131
Noncurrent deferred income taxes	2,882	0
Other long-term liabilities	3,882	3,523
Total liabilities	27,052	21,176
Total shareholders' equity	225,515	221,201
Total liabilities and shareholders' equity	252,567	242,377
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables, net of allowance for doubtful accounts	(3,618)	(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	(3,618)	(19)
Net property and equipment	(750)	(750)
Investments in subsidiaries	(1,230,016)	(1,153,438)
Intangible assets, net of amortization	0	0
Goodwill	0	0
Noncurrent deferred income taxes	(36,436)	(30,835)
Other long-term assets	0	0
Total assets	(1,270,820)	(1,185,042)
Current liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	(3,618)	(20)
Total current liabilities	(3,618)	(20)
Long-term debt, less current portion	0	0
Noncurrent deferred income taxes	(36,436)	(30,835)
Other long-term liabilities	0	0
Total liabilities	(40,054)	(30,855)
Total shareholders' equity	(1,230,766)	(1,154,187)
Total liabilities and shareholders' equity	$ (1,270,820)	$ (1,185,042)