Investment Securities (Summary of securities available for sale in an unrealized loss position) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule of Investments [Line Items]
Market Value, Less than 12 months	$ 36,494	$ 217,958
Unrealized Losses, Less than 12 months	183	733
Market Value, 12 months or longer	66,106	62,795
Unrealized Losses, 12 months or longer	68,543	68,124
U.S. Treasury securities and obligations of U.S. Government corporations and agencies [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	13,615	196,988
Unrealized Losses, Less than 12 months	1	12
Market Value, 12 months or longer	0	0
Unrealized Losses, 12 months or longer	0	0
State and political subdivisions [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	0	3,760
Unrealized Losses, Less than 12 months	0	25
Market Value, 12 months or longer	0	968
Unrealized Losses, 12 months or longer	0	13
Residential mortgage-backed securities, Agency [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	8,440	14,789
Unrealized Losses, Less than 12 months	38	175
Market Value, 12 months or longer	6,289	0
Unrealized Losses, 12 months or longer	47	0
Residential mortgage-backed securities, Non Agency [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	0	0
Unrealized Losses, Less than 12 months	0	0
Market Value, 12 months or longer	10,805	12,369
Unrealized Losses, 12 months or longer	5,491	2,592
Asset-backed Securities [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	13,861
Unrealized Losses, Less than 12 months	43
Market Value, 12 months or longer	0
Unrealized Losses, 12 months or longer	0
Trust preferred collateralized debt obligations [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	0	0
Unrealized Losses, Less than 12 months	0	0
Market Value, 12 months or longer	40,229	42,369
Unrealized Losses, 12 months or longer	59,412	61,792
Single issue trust preferred securities [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	0	412
Unrealized Losses, Less than 12 months	0	88
Market Value, 12 months or longer	7,714	6,956
Unrealized Losses, 12 months or longer	3,458	3,698
Marketable equity securities [Member]
Schedule of Investments [Line Items]
Market Value, Less than 12 months	578	2,009
Unrealized Losses, Less than 12 months	101	433
Market Value, 12 months or longer	1,069	133
Unrealized Losses, 12 months or longer	$ 135	$ 29