Commitments and Contingent liabilities - Schedule of Operating Lease and Contract Obligations (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Gross Lease Obligations [Member]
Sale Leaseback Transaction [Line Items]
Three months ending December 31, 2013	$ 8,014
Year ending December 31, 2014	30,170
Year ending December 31, 2015	28,346
Year ending December 31, 2016	27,877
Year ending December 31, 2017	27,262
Thereafter through December 31, 2027	108,318
Total Amount Of Lease & Contract Obligations	229,987
Sublease Income [Member]
Sale Leaseback Transaction [Line Items]
Three months ending December 31, 2013	525
Year ending December 31, 2014	1,868
Year ending December 31, 2015	1,494
Year ending December 31, 2016	1,464
Year ending December 31, 2017	1,541
Thereafter through December 31, 2027	358
Total Amount Of Lease & Contract Obligations	7,250
Net Lease Obligations [Member]
Sale Leaseback Transaction [Line Items]
Three months ending December 31, 2013	7,489
Year ending December 31, 2014	28,302
Year ending December 31, 2015	26,852
Year ending December 31, 2016	26,413
Year ending December 31, 2017	25,721
Thereafter through December 31, 2027	107,960
Total Amount Of Lease & Contract Obligations	$ 222,737