Segment Results (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net interest income		$ 325,573	$ 285,097	$ 653,439	$ 577,865
Provision for (recovery of) losses		895	334	719	341
Non-interest income	[1]	37,366	61,901	72,603	114,135
Non-interest expense	[2]	160,911	151,930	319,359	308,766
Income before income taxes		201,133	194,734	405,964	382,893
Income tax (benefit) expense		74,673	71,030	149,595	139,930
Net (loss) income		126,460	123,704	256,369	242,963
Identifiable segment assets (period-end)		49,035,747	48,648,532	49,035,747	48,648,532	$ 50,317,796
Operating Segments
Segment Reporting Information [Line Items]
Non-interest income		37,366	61,901	72,603	114,135
Banking Operations
Segment Reporting Information [Line Items]
Net interest income		321,663	280,006	646,580	569,291
Provision for (recovery of) losses		895	334	719	341
Non-interest income	[1]	29,899	45,355	60,485	78,509
Non-interest expense	[2]	144,152	135,476	286,202	275,627
Income before income taxes		202,198	185,490	411,715	363,601
Income tax (benefit) expense		75,097	67,246	151,912	132,136
Net (loss) income		127,101	118,244	259,803	231,465
Identifiable segment assets (period-end)		48,137,359	48,011,913	48,137,359	48,011,913
Banking Operations | Inter-segment
Segment Reporting Information [Line Items]
Non-interest income		(4,317)	(4,061)	(8,429)	(8,231)
Banking Operations | Operating Segments
Segment Reporting Information [Line Items]
Non-interest income		25,582	41,294	52,056	70,278
Residential Mortgage Banking
Segment Reporting Information [Line Items]
Net interest income		3,910	5,091	6,859	8,574
Non-interest income	[1]	7,467	16,546	12,118	35,626
Non-interest expense	[2]	16,759	16,454	33,157	33,139
Income before income taxes		(1,065)	9,244	(5,751)	19,292
Income tax (benefit) expense		(424)	3,784	(2,317)	7,794
Net (loss) income		(641)	5,460	(3,434)	11,498
Identifiable segment assets (period-end)		898,388	636,619	898,388	636,619
Residential Mortgage Banking | Inter-segment
Segment Reporting Information [Line Items]
Non-interest income		4,317	4,061	8,429	8,231
Residential Mortgage Banking | Operating Segments
Segment Reporting Information [Line Items]
Non-interest income		$ 11,784	$ 20,607	$ 20,547	$ 43,857

[1] Includes ancillary fee income.

[2] Includes both direct and indirect expenses.