Revenue from Contracts with Customer (Narrative) (Details) - Drilling [Member]	3 Months Ended
	Mar. 31, 2019 contract
Segment Reporting Information [Line Items]
Number of Contracts, Daywork	32
Short-term Contract with Customer [Member]
Segment Reporting Information [Line Items]
Contract Duration	2 months
Long-term Contract with Customer [Member]
Segment Reporting Information [Line Items]
Contract Duration	3 years