Investment Securities Held-to-Maturity - Company's Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Within one year, Amortized Cost	$ 37,216
After one but within five years, Amortized Cost	1,723,841
After five but within ten years, Amortized Cost	336,847
More than ten years, Amortized Cost	12,651
Amortized Cost	2,110,555	$ 2,046,647
Within one year, Fair Value	37,070
After one but within five years, Fair Value	1,696,173
After five but within ten years, Fair Value	328,635
More than ten years, Fair Value	12,565
Estimated Fair Value	$ 2,074,443	$ 1,991,421

Amount of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing in sixth through tenth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), with single maturity date and allocated without single maturity date, maturing in next fiscal year through fifth fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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-Publisher FASB
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