Available for Sale Debt Securities - Securities Available for Sale by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Securities available for sale, amortized cost	$ 965,135	$ 1,076,282
Securities available for sale, at fair value	976,919	$ 1,063,079
Available-for-sale Securities
Debt Securities, Available-for-sale [Line Items]
Due after one year through five years, amortized cost	3,003
Due after five years through ten years, amortized cost	25,936
Securities available for sale, amortized cost	28,939
Due after one year through five years, fair value	3,074
Due after five years through ten years, fair value	26,415
Securities available for sale, at fair value	$ 29,489

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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