Cash flow hedges (Detail) (Cash Flow Hedging [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (6,613)	$ 2,286	$ (13,509)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(6,091)	1,839	14,119
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	(109)	577	(44)
Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Income Statement Location of Gain (Loss) Reclassified from Accumulated OCI	Mortgage banking activities	Mortgage banking activities	Mortgage banking activities
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(6,613)	2,286	(13,509)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(6,091)	1,839	14,119
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	$ (109)	$ 577	$ (44)

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4D

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624177-113959

+ Details

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- Definition

The portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments representing (a) the amount of the hedge ineffectiveness and (b) the amount, if any, excluded from the assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 25

-Section 50

-Paragraph 1

-Subparagraph (a)(1),(2)

-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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- Definition

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References

+ Details

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- Definition

The income statement location of the effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

No definition available.

+ Details

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