Organization and Significant Accounting Policies - Business Description, Accounts Receivable and Allowance for Doubtful Accounts (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017 hospital business_segment	Sep. 30, 2017 business_segment	Dec. 31, 2017 hospital business_segment	Dec. 31, 2016
Business Description
Number of operating segments | business_segment	4	3	4
Number of outpatient clinics operated by the entity			1,616
Number of freestanding medical centers			312
Number of medical facilities			105
Number of department of veterans affairs community-based outpatient clinics			32
Number of states in which the entity had operations	47		47
Accounts Receivable and Allowance for Doubtful Accounts
Deductibles, co-payments and self-insured amounts as a percentage of net accounts receivable balance before doubtful accounts			0.60%	1.20%
Long term acute care
Business Description
Number of facilities operated by the entity			100
Inpatient rehabilitation
Business Description
Number of facilities operated by the entity			24