Securities - Available for Sale Securities Unrealized Losses (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]
Available for sale securities, Losses less than 12 months, Fair Value	$ 113,252	$ 481,937
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	839	9,460
Available for sale securities, Losses 12 months or longer, Fair value	165,959	49,064
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	6,211	2,914
Available for sale securities, Total, Fair value	279,211	531,001
Available for sale securities, Total, Gross Unrealized Losses	7,050	12,374
Equity securities [Member]
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]
Available for sale securities, Losses less than 12 months, Fair Value		3,282
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses		26
Available for sale securities, Losses 12 months or longer, Fair value	3	3
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	1	1
Available for sale securities, Total, Fair value	3	3,285
Available for sale securities, Total, Gross Unrealized Losses	1	27
U.S. Treasury and government agency securities [Member]
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]
Available for sale securities, Losses less than 12 months, Fair Value	163	205
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	1	1
Available for sale securities, Losses 12 months or longer, Fair value	25
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses
Available for sale securities, Total, Fair value	188	205
Available for sale securities, Total, Gross Unrealized Losses	1	1
Municipal obligations [Member]
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]
Available for sale securities, Losses less than 12 months, Fair Value		7,975
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses		25
Available for sale securities, Losses 12 months or longer, Fair value
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses
Available for sale securities, Total, Fair value		7,975
Available for sale securities, Total, Gross Unrealized Losses		25
Mortgage-backed securities [Member]
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]
Available for sale securities, Losses less than 12 months, Fair Value	64,485	376,350
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	514	7,164
Available for sale securities, Losses 12 months or longer, Fair value	125,977	49,061
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	4,811	2,913
Available for sale securities, Total, Fair value	190,462	425,411
Available for sale securities, Total, Gross Unrealized Losses	5,325	10,077
Collateralized mortgage obligations [Member]
Unrealized Loss And Fair Value Available For Sale Securities [Line Items]
Available for sale securities, Losses less than 12 months, Fair Value	48,604	94,125
Available for sale securities, Losses Less than 12 months, Gross Unrealized Losses	324	2,244
Available for sale securities, Losses 12 months or longer, Fair value	39,954
Available for sale securities, Losses 12 months or longer, Gross Unrealized Losses	1,399
Available for sale securities, Total, Fair value	88,558	94,125
Available for sale securities, Total, Gross Unrealized Losses	$ 1,723	$ 2,244