Segment Information - Information about Company's Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Net income (loss)	$ 241,613	$ 229,017
Business Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	24,811	24,973
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	96,423	98,841
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income (loss)	80,086	72,552
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income (loss)	5,954	11,360
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	31,965	18,580
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)	68,888	69,034
All Other [Member]
Segment Reporting Information [Line Items]
Net income (loss)	(66,514)	(66,323)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,099,791	1,076,540
Operating Segments [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	108,560	111,770
Operating Segments [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	246,581	249,349
Operating Segments [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	163,320	157,323
Operating Segments [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	15,474	24,657
Operating Segments [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	111,458	93,765
Operating Segments [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	300,391	306,780
Operating Segments [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Total revenues	154,007	132,896
Intersegment Activity Eliminated in Consolidated Totals [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	1,045	1,057
Intersegment Activity Eliminated in Consolidated Totals [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	1,085	1,197
Intersegment Activity Eliminated in Consolidated Totals [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	82	348
Intersegment Activity Eliminated in Consolidated Totals [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	(5,443)	(5,039)
Intersegment Activity Eliminated in Consolidated Totals [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	11,387	9,748
Intersegment Activity Eliminated in Consolidated Totals [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	3,137	3,505
Intersegment Activity Eliminated in Consolidated Totals [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Total revenues	$ (11,293)	$ (10,816)