Segment Information - Information about Company's Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Total revenues	$ 1,186,276	$ 1,039,633	$ 2,275,208	$ 2,036,745
Net income (loss)	348,466	233,380	622,579	439,843
Business Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	106,486	109,318	211,904	221,294
Inter-segment revenues	1,319	1,099	2,513	2,191
Net income (loss)	30,562	37,085	63,123	72,418
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	252,907	248,754	502,757	486,216
Inter-segment revenues	1,315	1,731	2,665	3,271
Net income (loss)	87,220	99,623	194,607	202,719
Commercial Real Estate [Member]
Segment Reporting Information [Line Items]
Total revenues	187,773	168,083	353,066	321,627
Inter-segment revenues	554	396	2,106	829
Net income (loss)	89,868	80,498	166,376	149,129
Discretionary Portfolio [Member]
Segment Reporting Information [Line Items]
Total revenues	(14,109)	(11,807)	(2,068)	(12,967)
Inter-segment revenues	(10,015)	(20,616)	(18,616)	(35,397)
Net income (loss)	(8,036)	(14,757)	(6,190)	(22,998)
Residential Mortgage Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	111,764	109,995	231,663	203,037
Inter-segment revenues	21,589	37,455	40,287	71,896
Net income (loss)	34,143	25,994	68,504	49,511
Retail Banking [Member]
Segment Reporting Information [Line Items]
Total revenues	292,837	313,994	584,022	620,842
Inter-segment revenues	3,598	3,198	6,855	6,090
Net income (loss)	51,500	58,191	103,850	106,848
All Other [Member]
Segment Reporting Information [Line Items]
Total revenues	248,618	101,296	393,864	196,696
Inter-segment revenues	(18,360)	(23,263)	(35,810)	(48,880)
Net income (loss)	$ 63,209	$ (53,254)	$ 32,309	$ (117,784)