Fair Value Measurements (Measured at Fair Value on a Nonrecurring Basis) (Details) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment losses related to property					$ (7,800)
Impairment loss	$ (7,700)	$ (2,400)	$ (15,000)	$ (10,120)	(15,257)	$ (98)
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant, and equipment, fair value disclosure					17,085
Property	$ 0			$ 0	17,085
Impairment losses related to property					(7,828)
Impairment loss					(7,828)
Fair Value, Measurements, Nonrecurring [Member] | Quoted Prices In Active Markets For Identical Assets And Liabilities (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property					0
Fair Value, Measurements, Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant, and equipment, fair value disclosure					12,901
Property					12,901
Fair Value, Measurements, Nonrecurring [Member] | Fair Value Using Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant, and equipment, fair value disclosure					4,184
Property					4,184
Carrying Value [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant, and equipment, fair value disclosure					24,900
Fair Value [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Property, plant, and equipment, fair value disclosure					$ 17,100