Changes in the Corporation's liability of estimated losses from credit recourses agreements (Detail) (Financial Guarantee Member, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Financial Guarantee Member
Guarantor Obligations [Line Items]
Balance as of beginning of period	$ 47,892	$ 45,892	$ 41,463	$ 51,673
Provision	9,189	5,180	28,215	15,965
Net charge-offs / terminations	(5,885)	(7,243)	(18,482)	(23,809)
Balance as of end of period	$ 51,196	$ 43,829	$ 51,196	$ 43,829