Allowance for Credit Losses - Summary of Provision for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Receivables [Abstract]
Provision for non-covered loans	$ 4,382	$ 0	$ 4,382	$ 4,949
Provision for covered loans	0	(5,671)	0	(5,671)
Total provision for loan losses	4,382	(5,671)	4,382	(722)
Provision for unfunded letters of credit	118	0	118	(951)
Total provision for credit losses	$ 4,500	$ (5,671)	$ 4,500	$ (1,673)