Summary of Significant Accounting Policies - Research and Engineering (Details) - In Process Research and Development - Two T D Drilling - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible Assets
Intangible Assets	$ 47.7
Transfer of research and development expenses to completed technology	$ 0.0	$ 0.0	$ 0.0