Organization and Significant Accounting Policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2017
Land improvements | Minimum
Property and equipment
Estimated useful lives	2 years
Land improvements | Maximum
Property and equipment
Estimated useful lives	25 years
Leasehold improvements | Minimum
Property and equipment
Estimated useful lives	1 year
Leasehold improvements | Maximum
Property and equipment
Estimated useful lives	15 years
Buildings
Property and equipment
Estimated useful lives	40 years
Building improvements | Minimum
Property and equipment
Estimated useful lives	5 years
Building improvements | Maximum
Property and equipment
Estimated useful lives	20 years
Furniture and equipment | Minimum
Property and equipment
Estimated useful lives	1 year
Furniture and equipment | Maximum
Property and equipment
Estimated useful lives	20 years