Revenue - Schedule of U.K. Revenue and Percentage Generated by Each Payor Type (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Revenue	$ 782,810	$ 760,617
U.K. Facilities [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Revenue	$ 273,593	$ 272,657
Revenue, Percentage	100.00%	100.00%
U.K. Facilities [Member] | U.K. Public Funded Sources [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Revenue	$ 246,136	$ 245,413
Revenue, Percentage	90.00%	90.00%
U.K. Facilities [Member] | Self-Pay [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Revenue	$ 26,915	$ 26,814
Revenue, Percentage	9.80%	9.80%
U.K. Facilities [Member] | Other [Member]
Health Care Organization, Receivable and Revenue Disclosures [Line Items]
Revenue	$ 542	$ 430
Revenue, Percentage	0.20%	0.20%