Investment Securities Held-to-Maturity - Company's Securities Held-to-Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Within one year, Amortized Cost	$ 70,980
After one but within five years, Amortized Cost	1,809,564
After five but within ten years, Amortized Cost	271,068
More than ten years, Amortized Cost	12,523
Amortized Cost	2,164,135	$ 2,046,647
Within one year, Fair Value	71,260
After one but within five years, Fair Value	1,829,087
After five but within ten years, Fair Value	275,192
More than ten years, Fair Value	12,926
Estimated Fair Value	$ 2,188,465	$ 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
-Name Accounting Standards Codification
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