Business Segments - Schedule of Financial Data for Business Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Average interest earning assets	$ 14,109,728				$ 12,814,236								$ 14,109,728	$ 12,814,236	$ 12,679,756
Interest income	162,969	167,230	166,858	174,136	166,572		171,639		167,794		167,819		671,193	673,824	676,812
Interest expense	44,440	45,408	44,787	46,677	48,258		49,704		50,124		50,927		181,312	199,013	214,060
Net interest income (loss)	118,529	121,822	122,071	127,459	118,314		121,935		117,670		116,892		489,881	474,811	462,752
Provision for credit losses	5,200	7,250	7,405	5,697	15,364		7,783		6,026		24,162		25,552	53,335	49,456
Net interest income (loss) after provision for credit losses													464,329	421,476	413,296
Non-interest income													120,946	112,297	91,327
Non-interest expense	95,623	93,219	91,510	94,548	84,869	[1]	85,794	[1]	83,572	[1]	84,321	[1]	374,900	338,556	319,688
Internal expense transfer
Income (loss) before income taxes	51,531	61,849	47,186	49,809	31,853	[1]	48,561	[1]	61,607	[1]	53,196	[1]	210,375	195,217	184,935
Return on average interest earning assets (pre-tax)	1.49%				1.52%								1.49%	1.52%	1.46%
Consumer Lending [Member]
Average interest earning assets	3,941,374				3,394,161								3,941,374	3,394,161	3,321,124
Interest income													174,978	171,939	180,432
Interest expense													45,499	47,832	51,240
Net interest income (loss)													129,479	124,107	129,192
Provision for credit losses													4,969	6,806	14,598
Net interest income (loss) after provision for credit losses													124,510	117,301	114,594
Non-interest income													83,765	45,830	52,545
Non-interest expense													69,281	56,884	49,758
Internal expense transfer													65,561	55,059	53,050
Income (loss) before income taxes													73,433	51,188	64,331
Return on average interest earning assets (pre-tax)	1.86%				1.51%								1.86%	1.51%	1.94%
Commercial Lending [Member]
Average interest earning assets	7,296,895				6,214,319								7,296,895	6,214,319	6,153,870
Interest income													407,288	375,873	355,565
Interest expense													84,234	87,574	94,944
Net interest income (loss)													323,054	288,299	260,621
Provision for credit losses													20,583	46,529	34,858
Net interest income (loss) after provision for credit losses													302,471	241,770	225,763
Non-interest income													(1,701)	16,965	7,927
Non-interest expense													54,963	48,829	42,131
Internal expense transfer													120,993	99,851	97,704
Income (loss) before income taxes													124,814	110,055	93,855
Return on average interest earning assets (pre-tax)	1.71%				1.77%								1.71%	1.77%	1.53%
Investment Management [Member]
Average interest earning assets	2,871,459				3,205,756								2,871,459	3,205,756	3,204,762
Interest income													96,582	132,530	146,851
Interest expense													33,148	45,176	49,445
Net interest income (loss)													63,434	87,354	97,406
Provision for credit losses
Net interest income (loss) after provision for credit losses													63,434	87,354	97,406
Non-interest income													6,817	7,381	6,166
Non-interest expense													1,219	1,016	992
Internal expense transfer													47,749	51,644	51,258
Income (loss) before income taxes													21,283	42,075	51,322
Return on average interest earning assets (pre-tax)	0.74%				1.31%								0.74%	1.31%	1.60%
Corporate and Other Adjustments [Member]
Average interest earning assets
Interest income													(7,655)	(6,518)	(6,036)
Interest expense													18,431	18,431	18,431
Net interest income (loss)													(26,086)	(24,949)	(24,467)
Provision for credit losses
Net interest income (loss) after provision for credit losses													(26,086)	(24,949)	(24,467)
Non-interest income													32,065	42,121	24,689
Non-interest expense													249,437	231,827	226,807
Internal expense transfer													(234,303)	(206,554)	(202,012)
Income (loss) before income taxes													$ (9,155)	$ (8,101)	$ (24,573)

[1] Previously reported amounts have been revised to reflect an increase in non-interest expense due to the immaterial correction of an error. See the "Correction of an Immaterial Error" section of Note 1 to the consolidated financial statements for additional information.