Guarantor/Non-Guarantor Condensed Consolidated Financial Statements - Balance Sheet (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 20,380	$ 86,197	$ 11,502	$ 22,011
Receivables, net of allowance	167,493	145,234
Intercompany receivable (payable)	0	0
Deferred income taxes	14,350	15,433
Inventory	13,211	11,184
Prepaid expenses and other current assets	13,333	11,564
Total current assets	228,767	269,612
Net property and equipment	939,445	793,956
Investments in subsidiaries	0	0
Intangible assets, net of amortization	48,205	52,680
Goodwill	41,683	41,683
Noncurrent deferred income taxes	1,242	735
Other long-term assets	12,066	14,088
Total assets	1,271,408	1,172,754	888,436
Current liabilities:
Accounts payable	95,189	66,440
Current portion of long-term debt	871	872
Prepaid drilling contracts	4,071	3,966
Accrued expenses	66,754	68,402
Total current liabilities	166,885	139,680
Long-term debt, less current portion	453,290	418,728
Noncurrent deferred income taxes	105,689	94,745
Other long-term liabilities	7,607	9,156
Total liabilities	733,471	662,309
Total shareholders' equity	537,937	510,445
Total liabilities and shareholders' equity	1,271,408	1,172,754
Parent [Member]
Current assets:
Cash and cash equivalents	20,768	91,932	10,802	15,737
Receivables, net of allowance	4	(2)
Intercompany receivable (payable)	(125,333)	(122,552)
Deferred income taxes	620	1,408
Inventory	0	0
Prepaid expenses and other current assets	1,197	285
Total current assets	(102,744)	(28,929)
Net property and equipment	2,301	1,605
Investments in subsidiaries	1,054,605	932,237
Intangible assets, net of amortization	59	171
Goodwill	0	0
Noncurrent deferred income taxes	41,608	30,835
Other long-term assets	10,611	11,949
Total assets	1,006,440	947,868
Current liabilities:
Accounts payable	1,092	1,090
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	13,381	16,779
Total current liabilities	14,473	17,869
Long-term debt, less current portion	453,170	417,747
Noncurrent deferred income taxes	0	921
Other long-term liabilities	110	137
Total liabilities	467,753	436,674
Total shareholders' equity	538,687	511,194
Total liabilities and shareholders' equity	1,006,440	947,868
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(3,665)	(13,879)	(3,723)	(1,840)
Receivables, net of allowance	124,591	112,531
Intercompany receivable (payable)	145,911	131,585
Deferred income taxes	6,704	8,644
Inventory	5,187	4,533
Prepaid expenses and other current assets	9,294	6,304
Total current assets	288,022	249,718
Net property and equipment	807,952	675,679
Investments in subsidiaries	223,940	221,201
Intangible assets, net of amortization	16,707	18,829
Goodwill	0	0
Noncurrent deferred income taxes	0	0
Other long-term assets	1,440	2,124
Total assets	1,338,061	1,167,551
Current liabilities:
Accounts payable	85,075	57,150
Current portion of long-term debt	850	850
Prepaid drilling contracts	2,726	1,297
Accrued expenses	44,420	45,012
Total current liabilities	133,071	104,309
Long-term debt, less current portion	0	850
Noncurrent deferred income taxes	145,902	124,659
Other long-term liabilities	4,483	5,496
Total liabilities	283,456	235,314
Total shareholders' equity	1,054,605	932,237
Total liabilities and shareholders' equity	1,338,061	1,167,551
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	3,277	8,144	4,423	8,114
Receivables, net of allowance	44,708	32,724
Intercompany receivable (payable)	(20,578)	(9,033)
Deferred income taxes	7,026	5,381
Inventory	8,024	6,651
Prepaid expenses and other current assets	2,842	4,975
Total current assets	45,299	48,842
Net property and equipment	129,942	117,422
Investments in subsidiaries	0	0
Intangible assets, net of amortization	31,439	33,680
Goodwill	41,683	41,683
Noncurrent deferred income taxes	1,242	735
Other long-term assets	15	15
Total assets	249,620	242,377
Current liabilities:
Accounts payable	9,022	8,200
Current portion of long-term debt	21	22
Prepaid drilling contracts	1,345	2,669
Accrued expenses	10,763	6,631
Total current liabilities	21,151	17,522
Long-term debt, less current portion	120	131
Noncurrent deferred income taxes	1,395	0
Other long-term liabilities	3,014	3,523
Total liabilities	25,680	21,176
Total shareholders' equity	223,940	221,201
Total liabilities and shareholders' equity	249,620	242,377
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables, net of allowance	(1,810)	(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	(1,810)	(19)
Net property and equipment	(750)	(750)
Investments in subsidiaries	(1,278,545)	(1,153,438)
Intangible assets, net of amortization	0	0
Goodwill	0	0
Noncurrent deferred income taxes	(41,608)	(30,835)
Other long-term assets	0	0
Total assets	(1,322,713)	(1,185,042)
Current liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	(1,810)	(20)
Total current liabilities	(1,810)	(20)
Long-term debt, less current portion	0	0
Noncurrent deferred income taxes	(41,608)	(30,835)
Other long-term liabilities	0	0
Total liabilities	(43,418)	(30,855)
Total shareholders' equity	(1,279,295)	(1,154,187)
Total liabilities and shareholders' equity	$ (1,322,713)	$ (1,185,042)