Detail of Certain Balance Sheet Accounts - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Capital expenditures incurred for purchase and construction of assets	$ 65,100
Accrued capital expenditures	8,630	$ 11,105	$ 8,800
Sold During Period
Property, Plant and Equipment [Line Items]
Land, building, and other equipment disposed of	20,700
Held-for-Sale
Property, Plant and Equipment [Line Items]
Land, building, and other equipment disposed of	17,400
Real Estate and Other Property and Equipment
Property, Plant and Equipment [Line Items]
Fixed assets acquired	23,000
Real Estate and Other Property and Equipment
Property, Plant and Equipment [Line Items]
Fixed assets acquired	$ 9,700