Business Segments - Reportable Business Segments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 666	$ 646	$ 1,314	$ 1,287
Noninterest income (expense)	205	188	460	402
Total revenue	871	834	1,774	1,689
Noninterest expense (income)	702	599	1,415	1,213
Credit expense (income)	(3)	(14)	(6)	(15)
Income before income taxes and including noncontrolling interests	172	249	365	491
Income tax expense (benefit)	34	67	84	118
Net income (loss) including noncontrolling interest	138	182	281	373
Deduct: Net loss from noncontrolling interests	3	5	7	9
Net income (loss) attributable to UNBC	141	187	288	382
Total assets, end of period-Market View	102,261	87,939	102,261	87,939	96,992
Retail Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	303	272	612	540
Noninterest income (expense)	60	58	120	114
Total revenue	363	330	732	654
Noninterest expense (income)	302	263	602	527
Credit expense (income)	7	6	13	12
Income before income taxes and including noncontrolling interests	54	61	117	115
Income tax expense (benefit)	21	24	46	45
Net income (loss) including noncontrolling interest	33	37	71	70
Net income (loss) attributable to UNBC	33	37	71	70
Total assets, end of period-Market View	31,081	26,459	31,081	26,459
Corporate Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	362	324	717	647
Noninterest income (expense)	166	151	323	300
Total revenue	528	475	1,040	947
Noninterest expense (income)	277	243	550	483
Credit expense (income)	39	38	77	77
Income before income taxes and including noncontrolling interests	212	194	413	387
Income tax expense (benefit)	52	50	101	102
Net income (loss) including noncontrolling interest	160	144	312	285
Net income (loss) attributable to UNBC	160	144	312	285
Total assets, end of period-Market View	44,736	36,377	44,736	36,377
Other [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	20	71	23	141
Noninterest income (expense)	(4)	(6)	49	18
Total revenue	16	65	72	159
Noninterest expense (income)	137	104	290	226
Credit expense (income)	(49)	(58)	(96)	(104)
Income before income taxes and including noncontrolling interests	(72)	19	(122)	37
Income tax expense (benefit)	(31)	2	(46)	(11)
Net income (loss) including noncontrolling interest	(41)	17	(76)	48
Deduct: Net loss from noncontrolling interests	3	5	7	9
Net income (loss) attributable to UNBC	(38)	22	(69)	57
Total assets, end of period-Market View	28,681	27,346	28,681	27,346
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)	(19)	(21)	(38)	(41)
Noninterest income (expense)	(17)	(15)	(32)	(30)
Total revenue	(36)	(36)	(70)	(71)
Noninterest expense (income)	(14)	(11)	(27)	(23)
Income before income taxes and including noncontrolling interests	(22)	(25)	(43)	(48)
Income tax expense (benefit)	(8)	(9)	(17)	(18)
Net income (loss) including noncontrolling interest	(14)	(16)	(26)	(30)
Net income (loss) attributable to UNBC	(14)	(16)	(26)	(30)
Total assets, end of period-Market View	$ (2,237)	$ (2,243)	$ (2,237)	$ (2,243)