Segment Information - Information about Company's Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Net income (loss)	$ 294,479	$ 293,462	$ 917,058	$ 733,305
Business Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	26,552	38,411	89,675	110,829
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	97,221	112,654	291,828	315,373
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income (loss)	79,450	75,896	245,826	225,025
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income (loss)	25,182	(5,039)	18,992	(28,037)
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	12,731	44,727	81,235	94,238
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	53,965	58,441	157,815	165,289
All Other [Member]
Segment Reporting Information [Line Items]
Net income (loss)	(622)	(31,628)	31,687	(149,412)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,150,496	1,108,455	3,425,704	3,145,200
Operating Segments [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	107,887	114,181	319,791	335,475
Operating Segments [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	257,317	255,498	760,074	741,714
Operating Segments [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	171,094	169,806	524,160	491,433
Operating Segments [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	44,040	1,805	41,972	(11,162)
Operating Segments [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	92,505	138,662	324,168	341,699
Operating Segments [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	314,273	318,567	898,295	939,409
Operating Segments [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Total revenues	163,380	109,936	557,244	306,632
Intersegment activity eliminated in consolidated totals [Member]
Segment Reporting Information [Line Items]
Total revenues
Intersegment activity eliminated in consolidated totals [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	1,237	1,011	3,750	3,202
Intersegment activity eliminated in consolidated totals [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	1,383	1,561	4,048	4,832
Intersegment activity eliminated in consolidated totals [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	399	5,031	2,505	5,860
Intersegment activity eliminated in consolidated totals [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	(19,584)	(25,593)	(38,200)	(60,990)
Intersegment activity eliminated in consolidated totals [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	15,241	28,454	55,528	100,350
Intersegment activity eliminated in consolidated totals [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	3,351	2,841	10,206	8,931
Intersegment activity eliminated in consolidated totals [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Total revenues	$ (2,027)	$ (13,305)	$ (37,837)	$ (62,185)