Fair Value Measurements - Impaired Loans Remeasured and Reported at Fair Value of Underlying Collateral (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	$ 68,202	$ 70,221
Specific valuation allowance allocations	(18,836)	$ (16,235)
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	2,161		$ 14,359
Specific valuation allowance allocations	1,179		(799)
Loans receivable, fair value disclosure	3,340		13,560
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying value of impaired loans before allocations	33,839		52,048
Specific valuation allowance allocations	(3,623)		(1,149)
Loans receivable, fair value disclosure	$ 30,216		$ 50,899