Summary of Provision for Credit Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Provision for non-covered loans	$ 7,582	$ 7,711	$ 20,385	$ 19,338
Provision for covered loans				18,094
Total provision for loan losses	7,582	7,711	20,385	37,432
Provision for unfunded letters of credit	(332)	72	(33)	539
Total provision for credit losses	$ 7,250	$ 7,783	$ 20,352	$ 37,971