Acquired Loans and Covered Loans (Detail) - Changes in Accretable Yield (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at the beginning of the year	$ 36,792		$ 51,498		$ 52,147
Additions	3,517		0		7,224
Accretion	(12,535)		(15,016)		(20,632)
Other	470	[1]	310	[1]	12,759	[1]
Balance at the end of the year	$ 28,244		$ 36,792		$ 51,498

[1] ncreases represent a rise in the expected future cash flows to be collected over the remaining estimated life of the underlying portfolio.