Segment Information - Information about Company's Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Net income (loss)	$ 275,344	$ 294,479	$ 788,697	$ 917,058
Business Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	30,905	26,552	87,263	89,675
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	101,740	97,221	306,863	291,828
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income (loss)	78,581	79,450	230,668	245,826
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income (loss)	8,279	25,182	34,538	18,992
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	25,021	12,731	72,144	81,235
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	32,901	53,965	94,646	157,815
Other Segments [Member]
Segment Reporting Information [Line Items]
Net income (loss)	(2,083)	(622)	(37,425)	31,687
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,120,170	1,150,496	3,322,236	3,425,704
Operating Segments [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	107,410	107,887	314,397	319,791
Operating Segments [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	249,124	257,317	750,206	760,074
Operating Segments [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	167,383	171,094	490,655	524,160
Operating Segments [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	17,881	44,040	72,450	41,972
Operating Segments [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	110,237	92,505	315,576	324,168
Operating Segments [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	274,117	314,273	804,499	898,295
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	194,018	163,380	574,453	557,244
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	1,082	1,237	3,359	3,750
Intersegment activity eliminated in consolidated totals [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	1,281	1,383	3,834	4,048
Intersegment activity eliminated in consolidated totals [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	442	399	1,315	2,505
Intersegment activity eliminated in consolidated totals [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	(5,478)	(19,584)	(15,799)	(38,200)
Intersegment activity eliminated in consolidated totals [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	12,875	15,241	34,395	55,528
Intersegment activity eliminated in consolidated totals [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	3,735	3,351	11,137	10,206
Intersegment activity eliminated in consolidated totals [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	$ (13,937)	$ (2,027)	$ (38,241)	$ (37,837)