Revenue from Contracts with Customers Revenue from Contracts with Customer (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) contract	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Retained earnings	$ 805,993	$ 798,128	$ 799,402
Number of Contracts, Daywork | contract	32
Oil and Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenue Satisfied at Point in Time, Transfer of Control	Revenues from sales are recognized when the customer obtains control of the company’s product. For sales to other midstream and downstream oil and gas companies, this would occur at a point in time, typically on delivery to the customer.
Drilling [Member]
Segment Reporting Information [Line Items]
Revenue Satisfied over Time, Method Used	At inception, the total transaction price will be estimated to include any applicable fixed consideration, unconstrained variable consideration (estimated day rate mobilization and demobilization revenue, estimated operating day rate revenue to be earned over the contract term, expected bonuses (if material and can be reasonably estimated without significant reversal), and penalties (if material and can be reasonably estimated without significant reversal)). Allocation rules under the new standard will allow the company to recognize revenues associated with contract drilling contacts in materially the same manner as under the previous revenue accounting standard. A contract liability will be recorded for consideration received before the corresponding transfer of services. Such liabilities will generally only arise in relation to upfront mobilization fees which are paid in advance and are allocated/recognized over the entire performance obligation. Such balances will be amortized over the recognition period based on the same method of measure used for revenue.
Revenue, Practical Expedient, Initial Application and Transition, Qualitative Assessment	The majority of contract drilling contracts have an original term of less than one year; however, there are a few contracts with a longer duration that are not material.
Mid-Stream [Member]
Segment Reporting Information [Line Items]
Revenue Satisfied over Time, Method Used	Contract terms can range from single month to extended term contracts spanning a decade or more, some include evergreen provisions. Fees for mid-stream services (gathering, transportation, processing) are performance obligations and meet the criteria of over time recognition which could be considered a series of distinct performance obligations that represents one overall performance obligation of gas gathering and processing services.
Revenue, Practical Expedient, Initial Application and Transition, Qualitative Assessment	As stated previously, the contract term for mid-stream services is typically longer than one year. However, based on the guidance at 606-10-32-40, we determined some of the variable payment in mid-stream service agreements specifically relates to the entity’s efforts to satisfy the performance obligation and that “allocating the variable amount entirely to the distinct good or service is consistent with the allocation objective in paragraph 606-10-32-28.” Therefore, the practical expedient relates to this variable consideration: the commodity fee and the gathering fee.
Minimum [Member] | Drilling [Member]
Segment Reporting Information [Line Items]
Contract Duration	6 months
Number of Days for Drilling of Wells	10 days
Minimum [Member] | Mid-Stream [Member]
Segment Reporting Information [Line Items]
Contract Duration	5 years
Remaining Term of Contract	4 years
Maximum [Member] | Drilling [Member]
Segment Reporting Information [Line Items]
Contract Duration	2 years
Number of Days for Drilling of Wells	90 days
Maximum [Member] | Mid-Stream [Member]
Segment Reporting Information [Line Items]
Contract Duration	10 years
Remaining Term of Contract	5 years
Short-term Contract with Customer [Member] | Drilling [Member]
Segment Reporting Information [Line Items]
Contract Duration	2 months
Long-term Contract with Customer [Member]
Segment Reporting Information [Line Items]
Number of Contracts, Daywork | contract	6
Long-term Contract with Customer [Member] | Drilling [Member]
Segment Reporting Information [Line Items]
Contract Duration	14 months
Adjustments due to ASC606 [Member] | Oil and Natural Gas [Member]
Segment Reporting Information [Line Items]
Retained earnings		0
Adjustments due to ASC606 [Member] | Drilling [Member]
Segment Reporting Information [Line Items]
Retained earnings		0
Adjustments due to ASC606 [Member] | Mid-Stream [Member]
Segment Reporting Information [Line Items]
Retained earnings	$ (374)
Adjustment to opening retained earnings, before tax		(1,700)
Adjustment to opening retained earnings, after tax		$ (1,274)
Gathering service contracts [Member] | Minimum [Member] | Mid-Stream [Member]
Segment Reporting Information [Line Items]
Remaining Term of Contract	1 year
Gathering service contracts [Member] | Maximum [Member] | Mid-Stream [Member]
Segment Reporting Information [Line Items]
Remaining Term of Contract	15 years