Commitments and Contingent liabilities - Schedule of Operating Lease and Contract Obligations (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Gross Lease Obligations [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Year ending December 31, 2015	$ 28,224
Year ending December 31, 2016	27,762
Year ending December 31, 2017	26,211
Year ending December 31, 2018	25,354
Year ending December 31, 2019	23,316
Thereafter through December 31, 2027	64,441
Total	195,308
Sublease Income [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Year ending December 31, 2015	4,056
Year ending December 31, 2016	3,488
Year ending December 31, 2017	2,983
Year ending December 31, 2018	2,667
Year ending December 31, 2019	2,389
Thereafter through December 31, 2027	10,244
Total	25,827
Net Lease Obligations [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Year ending December 31, 2015	24,168
Year ending December 31, 2016	24,274
Year ending December 31, 2017	23,228
Year ending December 31, 2018	22,687
Year ending December 31, 2019	20,927
Thereafter through December 31, 2027	54,197
Total	$ 169,481

Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

-Paragraph 40

-Subparagraph (Note 3)

-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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