Merger, Integration and Other Costs (Summary of Merger and Restructuring Costs) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Merger Integration And Other Costs [Abstract]
Merger costs	$ 10,261
Restructuring costs:
Termination benefits	8,558
Professional services	302
Other	134
Total restructuring costs	8,994
Total merger and restructuring costs	$ 19,255	[1]

[1] For integration and restructuring costs related to the merger with Deltic see Note 14: Merger, Integration and Other Costs.