Guarantor/Non-Guarantor Condensed Consolidated Financial Statements - Balance Sheet (Unaudited) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Current assets:
Cash and cash equivalents	$ 86,197	$ 22,011	$ 40,379	$ 26,821
Short-term investments	0	12,569
Receivables, net of allowance for doubtful accounts	145,234	89,515
Intercompany receivable (payable)	0	0
Deferred income taxes	15,433	9,867
Inventory	11,184	9,023
Prepaid expenses and other current assets	11,564	8,797
Total current assets	269,612	151,782
Net property and equipment	793,956	655,508
Investments in subsidiaries	0	0
Intangible assets, net of amortization	52,680	21,966
Goodwill	41,683	0
Noncurrent deferred income taxes	735	0
Other long-term assets	14,088	12,087
Total assets	1,172,754	841,343	824,955
Current liabilities:
Accounts payable	66,440	26,929
Current portion of long-term debt	872	1,408
Prepaid drilling contracts	3,966	3,669
Accrued expenses	68,402	43,634
Total current liabilities	139,680	75,640
Long-term debt, less current portion	418,728	279,530
Noncurrent deferred income taxes	94,745	80,160
Other long-term liabilities	9,156	9,680
Total liabilities	662,309	445,010
Total shareholders' equity	510,445	396,333	421,448	414,118
Total liabilities and shareholders' equity	1,172,754	841,343
Parent [Member]
Current assets:
Cash and cash equivalents	91,932	15,737	33,352	858
Short-term investments		12,569
Receivables, net of allowance for doubtful accounts	(2)	0
Intercompany receivable (payable)	(122,552)	(80,900)
Deferred income taxes	1,408	178
Inventory	0	0
Prepaid expenses and other current assets	285	263
Total current assets	(28,929)	(52,153)
Net property and equipment	1,605	1,601
Investments in subsidiaries	932,237	714,292
Intangible assets, net of amortization	171	235
Goodwill	0
Noncurrent deferred income taxes	30,835	14,632
Other long-term assets	11,949	6,739
Total assets	947,868	685,346
Current liabilities:
Accounts payable	1,090	242
Current portion of long-term debt	0	63
Prepaid drilling contracts	0	0
Accrued expenses	16,779	9,861
Total current liabilities	17,869	10,166
Long-term debt, less current portion	417,747	277,830
Noncurrent deferred income taxes	921	0
Other long-term liabilities	137	267
Total liabilities	436,674	288,263
Total shareholders' equity	511,194	397,083
Total liabilities and shareholders' equity	947,868	685,346
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	(13,879)	(1,840)	(2,716)	13,896
Short-term investments		0
Receivables, net of allowance for doubtful accounts	112,531	78,575
Intercompany receivable (payable)	131,585	80,942
Deferred income taxes	8,644	4,167
Inventory	4,533	2,874
Prepaid expenses and other current assets	6,304	4,604
Total current assets	249,718	169,322
Net property and equipment	675,679	562,390
Investments in subsidiaries	221,201	114,483
Intangible assets, net of amortization	18,829	21,731
Goodwill	0
Noncurrent deferred income taxes	0	0
Other long-term assets	2,124	2,844
Total assets	1,167,551	870,770
Current liabilities:
Accounts payable	57,150	20,134
Current portion of long-term debt	850	1,345
Prepaid drilling contracts	1,297	1,000
Accrued expenses	45,012	30,786
Total current liabilities	104,309	53,265
Long-term debt, less current portion	850	1,700
Noncurrent deferred income taxes	124,659	94,769
Other long-term liabilities	5,496	6,744
Total liabilities	235,314	156,478
Total shareholders' equity	932,237	714,292
Total liabilities and shareholders' equity	1,167,551	870,770
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	8,144	8,114	9,743	12,067
Short-term investments		0
Receivables, net of allowance for doubtful accounts	32,724	10,940
Intercompany receivable (payable)	(9,033)	(42)
Deferred income taxes	5,381	5,522
Inventory	6,651	6,149
Prepaid expenses and other current assets	4,975	3,930
Total current assets	48,842	34,613
Net property and equipment	117,422	92,267
Investments in subsidiaries	0	0
Intangible assets, net of amortization	33,680	0
Goodwill	41,683
Noncurrent deferred income taxes	735	0
Other long-term assets	15	2,504
Total assets	242,377	129,384
Current liabilities:
Accounts payable	8,200	6,553
Current portion of long-term debt	22	0
Prepaid drilling contracts	2,669	2,669
Accrued expenses	6,631	2,987
Total current liabilities	17,522	12,209
Long-term debt, less current portion	131	0
Noncurrent deferred income taxes	0	23
Other long-term liabilities	3,523	2,669
Total liabilities	21,176	14,901
Total shareholders' equity	221,201	114,483
Total liabilities and shareholders' equity	242,377	129,384
Eliminations [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Short-term investments		0
Receivables, net of allowance for doubtful accounts	(19)	0
Intercompany receivable (payable)	0	0
Deferred income taxes	0	0
Inventory	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(19)	0
Net property and equipment	(750)	(750)
Investments in subsidiaries	(1,153,438)	(828,775)
Intangible assets, net of amortization	0	0
Goodwill	0
Noncurrent deferred income taxes	(30,835)	(14,632)
Other long-term assets	0	0
Total assets	(1,185,042)	(844,157)
Current liabilities:
Accounts payable	0	0
Current portion of long-term debt	0	0
Prepaid drilling contracts	0	0
Accrued expenses	(20)	0
Total current liabilities	(20)	0
Long-term debt, less current portion	0	0
Noncurrent deferred income taxes	(30,835)	(14,632)
Other long-term liabilities	0	0
Total liabilities	(30,855)	(14,632)
Total shareholders' equity	(1,154,187)	(829,525)
Total liabilities and shareholders' equity	$ (1,185,042)	$ (844,157)