Segment Reporting (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Revenue, Net	$ 254,455,000	$ 245,428,000	$ 247,006,000	$ 234,191,000	$ 243,786,000	$ 231,344,000	$ 225,785,000	$ 206,733,000	$ 981,080,000	$ 907,648,000	$ 794,653,000
Segment Reporting Information, Intersegment Revenue									0	0	0
Income Before Interest Expense and Taxes	75,868,000	75,380,000	72,126,000	73,906,000	72,888,000	63,564,000	57,803,000	56,499,000	297,280,000	250,754,000	226,926,000
Assets	636,516,000				610,873,000				636,516,000	610,873,000	650,241,000
Payments to Acquire Property, Plant, and Equipment									31,151,000	29,927,000	27,569,000
Depreciation and amortization									22,917,000	23,303,000	23,113,000
Operating Segment Reservoir Description [Member]
Segment Reporting Information [Line Items]
Revenue, Net									495,529,000	469,775,000	425,829,000
Segment Reporting Information, Intersegment Revenue									2,484,000	1,515,000	1,817,000
Income Before Interest Expense and Taxes									144,502,000	116,244,000	106,179,000
Assets	293,974,000				270,270,000				293,974,000	270,270,000	267,621,000
Payments to Acquire Property, Plant, and Equipment									16,987,000	15,320,000	20,495,000
Depreciation and amortization									14,094,000	14,073,000	13,988,000
Operating Segment Production Enhancement [Member]
Segment Reporting Information [Line Items]
Revenue, Net									403,792,000	371,449,000	313,956,000
Segment Reporting Information, Intersegment Revenue									2,757,000	1,947,000	1,681,000
Income Before Interest Expense and Taxes									128,602,000	112,576,000	101,241,000
Assets	242,254,000				221,599,000				242,254,000	221,599,000	196,802,000
Payments to Acquire Property, Plant, and Equipment									7,423,000	8,700,000	5,066,000
Depreciation and amortization									6,139,000	6,449,000	6,442,000
Operating Segment Reservoir Management [Member]
Segment Reporting Information [Line Items]
Revenue, Net									81,759,000	66,424,000	54,868,000
Segment Reporting Information, Intersegment Revenue									1,492,000	1,686,000	1,625,000
Income Before Interest Expense and Taxes									26,428,000	21,887,000	19,759,000
Assets	34,532,000				26,070,000				34,532,000	26,070,000	24,313,000
Payments to Acquire Property, Plant, and Equipment									920,000	1,318,000	591,000
Depreciation and amortization									731,000	666,000	713,000
Operating Segment Corporate And Other [Member]
Segment Reporting Information [Line Items]
Revenue, Net									0	0	0
Segment Reporting Information, Intersegment Revenue									(6,733,000)	(5,148,000)	(5,123,000)
Income Before Interest Expense and Taxes									(2,252,000)	47,000	(253,000)
Assets	65,756,000				92,934,000				65,756,000	92,934,000	161,505,000
Payments to Acquire Property, Plant, and Equipment									5,821,000	4,589,000	1,417,000
Depreciation and amortization									$ 1,953,000	$ 2,115,000	$ 1,970,000