Segment Information - Summary of Financial Information by Operating Segment, Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Assets:
Assets	$ 6,684,499	$ 4,279,208
U.S. Facilities [Member]
Assets:
Assets	3,330,105	3,061,519
U.K. Facilities [Member]
Assets:
Assets	3,179,240	1,045,922
Corporate and Other [Member]
Assets:
Assets	$ 175,154	$ 171,767