Summary of Significant Accounting Policies - Property, Plant, Equipment and Depreciation (Details)	12 Months Ended
	Dec. 31, 2017
Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Useful life	25 years
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Useful life	15 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Useful life	35 years
Land Improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Land Improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful life	30 years