Segment Information - Summary of Financial Information by Operating Segment, Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets:
Assets	$ 6,717,995	$ 6,879,142
U.S. Facilities [Member] | Operating Segment [Member]
Assets:
Assets	4,083,825	4,037,968
U.K. Facilities [Member] | Operating Segment [Member]
Assets:
Assets	2,443,498	2,610,357
Corporate and Other [Member] | Corporate Reconciling Items and Eliminations [Member]
Assets:
Assets	$ 190,672	$ 230,817