Annual report pursuant to Section 13 and 15(d)

Investments in Marketable Securities - Amortized Cost and Fair Value of Investments in Available for Sale Securities Unrealized Loss Position (Detail)

v3.20.4
Investments in Marketable Securities - Amortized Cost and Fair Value of Investments in Available for Sale Securities Unrealized Loss Position (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities continuous unrealized loss position for less than 12 months, fair value $ 72,058 $ 47,823
Available for sale securities continuous unrealized loss position for less than 12 months, gross unrealized loss (45) (21)
Available for sale securities continuous unrealized loss position for 12 months or longer, fair value 157 566
Available for sale securities continuous unrealized loss position for 12 months or longer, gross unrealized loss (5) (1)
Available for sale securities continuous unrealized loss position, fair value 72,215 48,389
Available for sale securities continuous unrealized loss position, gross unrealized loss (50) (22)
U.S. Treasuries [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities continuous unrealized loss position for less than 12 months, fair value 41,702 39,823
Available for sale securities continuous unrealized loss position for less than 12 months, gross unrealized loss (5) (5)
Available for sale securities continuous unrealized loss position for 12 months or longer, fair value 0 0
Available for sale securities continuous unrealized loss position for 12 months or longer, gross unrealized loss 0 0
Available for sale securities continuous unrealized loss position, fair value 41,702 39,823
Available for sale securities continuous unrealized loss position, gross unrealized loss (5) (5)
U.S. Government Sponsored Entities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities continuous unrealized loss position for less than 12 months, fair value   0
Available for sale securities continuous unrealized loss position for less than 12 months, gross unrealized loss   0
Available for sale securities continuous unrealized loss position for 12 months or longer, fair value   566
Available for sale securities continuous unrealized loss position for 12 months or longer, gross unrealized loss   (1)
Available for sale securities continuous unrealized loss position, fair value   566
Available for sale securities continuous unrealized loss position, gross unrealized loss   (1)
Corporate debt [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities continuous unrealized loss position for less than 12 months, fair value 29,810 6,029
Available for sale securities continuous unrealized loss position for less than 12 months, gross unrealized loss (34) (3)
Available for sale securities continuous unrealized loss position for 12 months or longer, fair value 0 0
Available for sale securities continuous unrealized loss position for 12 months or longer, gross unrealized loss 0 0
Available for sale securities continuous unrealized loss position, fair value 29,810 6,029
Available for sale securities continuous unrealized loss position, gross unrealized loss (34) (3)
ABS and other [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available for sale securities continuous unrealized loss position for less than 12 months, fair value 546 1,971
Available for sale securities continuous unrealized loss position for less than 12 months, gross unrealized loss (6) (13)
Available for sale securities continuous unrealized loss position for 12 months or longer, fair value 157 0
Available for sale securities continuous unrealized loss position for 12 months or longer, gross unrealized loss (5) 0
Available for sale securities continuous unrealized loss position, fair value 703 1,971
Available for sale securities continuous unrealized loss position, gross unrealized loss $ (11) $ (13)