Basis of Presentation of Interim Period Statements - Schedule of Reconciles of Cash, Cash Equivalents and Restricted Cash Balances (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 2,469	$ 68,688	$ 62,210	$ 44,570
Restricted cash, included in restricted cash and investments	11,694	165,149	93,320	228,771
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 14,163	$ 233,837	$ 155,530	$ 273,341