Derivatives and Hedging Activities - Summary of Cash Flow Hedges (Detail) - Cash flow hedges [Member] - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Notional Amount, Derivative assets	$ 626,012	$ 72,262
Notional Amount, Derivative liabilities	135,194	440,637
Notional Amount, Total	761,206	512,899
Fair Value, Derivative assets	29,965	2,379
Fair Value, Derivative liabilities	(3,549)	(29,777)
Fair Value, Total	26,416	(27,398)
Accumulated Other Comprehensive Income (Loss) [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Derivative assets	23,770	2,055
Fair Value, Derivative liabilities	(6,190)	(34,311)
Fair Value, Total	17,580	(32,256)
Net gain (loss) to be reclassified within 12 months	$ 11,000	$ (26,700)

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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Fair value of all asset derivatives designated as cash flow hedging instruments.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(1)
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Fair value of all liability derivatives designated as cash flow hedging instruments.

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Net fair value of all derivative instruments designated as cash flow hedging instruments, which is ordinarily reflected within other comprehensive income.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
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Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
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Nominal or face amount used to calculate payments on the derivative liability.

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The estimated net amount of unrealized gains or losses on foreign currency cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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