Investment Securities - Pooled Trust Preferred Securities (Detail) (USD $) In Thousands, unless otherwise specified				6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Jun. 30, 2013 Pooled Trust Preferred Securities One [Member]	Jun. 30, 2013 Pooled Trust Preferred Securities One [Member] MM Community Funding IX [Member] Item	Jun. 30, 2013 Pooled Trust Preferred Securities One [Member] Reg Div Funding 2004 [Member] Item	Jun. 30, 2013 Pooled Trust Preferred Securities One [Member] Pretsl XII [Member] Item	Jun. 30, 2013 Pooled Trust Preferred Securities One [Member] Pretsl XXVII LTD [Member] Item	Jun. 30, 2013 Pooled Trust Preferred Securities One [Member] Trapeza Ser 13A [Member] Item	Jun. 30, 2013 Single Issuer Trust Preferred Securities [Member]	Jun. 30, 2013 Single Issuer Trust Preferred Securities [Member] First Empire Cap (M&T) [Member]	Jun. 30, 2013 Single Issuer Trust Preferred Securities [Member] First Empire Cap (M&T) [Member]	Jun. 30, 2013 Single Issuer Trust Preferred Securities [Member] Fleet Cap Tr V (BOA) [Member]	Jun. 30, 2013 Single Issuer Trust Preferred Securities [Member] JP Morgan Chase Cap XIII [Member]	Jun. 30, 2013 Single Issuer Trust Preferred Securities [Member] NB-Global [Member]	Jun. 30, 2013 Trust Preferred Securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities [Line Items]
Pooled trust preferred securities, Class					B-2	B-2	B-1	B	A2A
Lowest Credit Rating					CC	D	C	CC	B		BB+	BB+	Ba2	BBB	BB
Amortized Cost				$ 23,061	$ 2,067	$ 4,012	$ 2,696	$ 4,872	$ 9,414	$ 12,692	$ 958	$ 2,910	$ 3,369	$ 4,729	$ 726	$ 35,753
Available-for-sale securities, Fair Value	2,659,084	2,500,784	2,208,262	9,152	888	938	1,350	1,402	4,574	11,595	990	2,970	2,800	4,050	785	20,747
Available-for-sale, Unrealized Losses	73,664	19,880		(13,909)	(1,179)	(3,074)	(1,346)	(3,470)	(4,840)	(1,097)	32	60	(569)	(679)	59	(15,006)
Realized Losses
# of Issuers Currently Performing					14	23	48	33	41
# of Issuers Currently Remaining					27	43	71	47	51
Actual Deferrals and Defaults as a Percent of Original Collateral					32.00%	40.70%	24.80%	25.10%	27.60%
Expected Defaults as a % of Remaining Performing Collateral					5.40%	6.10%	6.90%	18.80%	18.30%
Excess Subordination as a % of Current Performing Collateral					0.00%	0.00%	0.00%	30.90%	46.50%