Investment Securities (Schedule of Realized Gain (Loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Realized gains on investment securities	$ 530	$ 6	$ 547	$ 6
Realized losses on investment securities	(7)	(26)	(91)	(1,001)
Net realized gains (losses) on investment securities	523	(20)	456	(995)
Unrealized gains on equity securities with readily determinable fair value	703	229	2,134	2,102
Unrealized losses on equity securities with readily determinable fair value	(209)	(222)	(209)	(1,065)
Net unrealized gains on equity securities with readily determinable fair value	494	7	1,925	1,037
Upward adjustments of equity securities without readily determinable fair values	110	25	110	156
Downward adjustments of equity securities without readily determinable fair values	0	0		0
Impairment of equity securities without readily determinable fair values	(263)	0	(263)	(537)
Adjustment and impairment, net, of equity securities without readily determinable fair values	(153)	25	(153)	(381)
Other than temporary impairment charges	0	0	0	0
Gains (losses) on investment securities, net	864	12	2,228	(339)
Proceeds from sales of available-for-sale securities	404,462	0	667,918	208,991
Proceeds from sales of equity securities with readily determinable fair value	11,000	0	11,000	0
Proceeds from sales and capital distributions of equity securities without readily determinable fair value	$ 396	$ 616	$ 609	$ 616

Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
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Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of loss from downward price adjustment on investment in equity security without readily determinable fair value.

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Amount of impairment loss on investment in equity security without readily determinable fair value.

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Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value.

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The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

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Amount of realized gain (loss) on investment in marketable security, excluding other-than-temporary impairment (OTTI).

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Amount of cash inflow from sale 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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Gross realized gains on marketable securities.

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Gross losses on marketable securities

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Proceeds from Sales and Capital Distributions of Equity Securities Without Readily Determinable Fair Value

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Securities Owned Not Readily Marketable, Period Increase (Decrease)

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