Segment Information - Summary of Prior Period Financial Information Restated (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net income (loss)	$ 1,079,667	$ 1,066,246	$ 1,138,480
Business Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		99,270	101,065
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		402,928	407,393
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income (loss)		315,960	329,286
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income (loss)		48,343	32,236
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		84,542	92,323
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		273,358	320,950
All Other [Member]
Segment Reporting Information [Line Items]
Net income (loss)		(158,155)	(144,773)
Net Income (Loss) as Previously Reported [Member]
Segment Reporting Information [Line Items]
Net income (loss)		1,066,246	1,138,480
Net Income (Loss) as Previously Reported [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		119,809	111,040
Net Income (Loss) as Previously Reported [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		411,139	391,340
Net Income (Loss) as Previously Reported [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income (loss)		316,129	321,793
Net Income (Loss) as Previously Reported [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income (loss)		48,098	29,968
Net Income (Loss) as Previously Reported [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		95,006	99,392
Net Income (Loss) as Previously Reported [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		119,916	182,401
Net Income (Loss) as Previously Reported [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Net income (loss)		(43,851)	2,546
Impact of Changes [Member] | Business Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		(20,539)	(9,975)
Impact of Changes [Member] | Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		(8,211)	16,053
Impact of Changes [Member] | Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Net income (loss)		(169)	7,493
Impact of Changes [Member] | Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Net income (loss)		245	2,268
Impact of Changes [Member] | Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		(10,464)	(7,069)
Impact of Changes [Member] | Retail Banking [Member]
Segment Reporting Information [Line Items]
Net income (loss)		153,442	138,549
Impact of Changes [Member] | All Other [Member]
Segment Reporting Information [Line Items]
Net income (loss)		$ (114,304)	$ (147,319)