Summary of Cash and Cash Equivalents and Restricted Cash Balances (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Cash and cash equivalents	$ 39,139	$ 42,453	$ 84,483
Restricted cash	65,000	$ 63,067	152,962
Total cash and cash equivalents and restricted cash	$ 104,139		$ 237,445