Organization and Significant Accounting Policies - Intangible Assets (Details) - business_segment	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2017
Intangible Assets and Liabilities
Number of operating segments	4	3	4
Customer relationships | Minimum
Intangible Assets and Liabilities
Useful life of intangible assets			6 years
Customer relationships | Maximum
Intangible Assets and Liabilities
Useful life of intangible assets			17 years
Favorable leasehold interests | Minimum
Intangible Assets and Liabilities
Useful life of intangible assets			1 year
Favorable leasehold interests | Maximum
Intangible Assets and Liabilities
Useful life of intangible assets			15 years
Non-compete agreements | Minimum
Intangible Assets and Liabilities
Useful life of intangible assets			1 year
Non-compete agreements | Maximum
Intangible Assets and Liabilities
Useful life of intangible assets			15 years