Commitments and Contingent liabilities - Schedule of Lease and Contract Obligations (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Gross Lease Obligations [Member]
Sale Leaseback Transaction [Line Items]
Six months ending December 31, 2013	$ 11,349
Year ending December 31, 2014	21,721
Year ending December 31, 2015	20,722
Year ending December 31, 2016	20,196
Year ending December 31, 2017	20,022
Thereafter through August 31, 2023	78,825
Total Amount Of Lease & Contract Obligations	172,835
Sublease Income [Member]
Sale Leaseback Transaction [Line Items]
Six months ending December 31, 2013	1,179
Year ending December 31, 2014	1,771
Year ending December 31, 2015	1,376
Year ending December 31, 2016	1,333
Year ending December 31, 2017	1,412
Thereafter through August 31, 2023	192
Total Amount Of Lease & Contract Obligations	7,263
Net Lease Obligations [Member]
Sale Leaseback Transaction [Line Items]
Six months ending December 31, 2013	10,170
Year ending December 31, 2014	19,950
Year ending December 31, 2015	19,346
Year ending December 31, 2016	18,863
Year ending December 31, 2017	18,610
Thereafter through August 31, 2023	78,633
Total Amount Of Lease & Contract Obligations	$ 165,572