Summary of Cash, Cash Equivalents and Restricted Cash Reported In Condensed Consolidated Statements of Cash Flows (Detail) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash And Cash Equivalents Period Increase Decrease [Abstract]
Cash and cash equivalents		$ 73,053	$ 74,423
Restricted cash	[1]	93,163	92,874
Total cash, cash equivalents and restricted cash		$ 166,216	$ 167,297	$ 151,278	$ 121,950

[1] Restricted cash, associated with an insurance subsidiary, is included in other assets on the accompanying consolidated balance sheet.