Operating Segment Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2012 store	Mar. 31, 2011
Segment Reporting Information [Line Items]
Net interest income	$ 442,299,000	$ 423,856,000
Provision for loan losses	15,664,000	60,000,000
Net interest income after provision for loan losses	426,635,000	363,856,000
Net impairment losses on investment securities	(10,209,000)	(3,105,000)
Other noninterest income	4,045,000	20,966,000
Noninterest expense	392,372,000	408,375,000
Income (loss) before income taxes	141,262,000	89,624,000
Income tax expense (benefit)	51,859,000	37,033,000
Net income (loss)	89,403,000	52,591,000
Net income (loss) applicable to noncontrolling interests	(273,000)	(226,000)
Net income (loss) applicable to controlling interest	89,676,000	52,817,000
Preferred stock dividends	(38,953,000)	(32,777,000)
Net earnings (loss) applicable to common shareholders	25,489,000	14,767,000
Number of community/regional banks operating in distinct geographical areas	8
Zions Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	172,600,000	172,600,000
Provision for loan losses	40,500,000	39,000,000
Net interest income after provision for loan losses	132,100,000	133,600,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent
Other noninterest income	55,300,000	49,500,000
Noninterest expense	122,000,000	128,400,000
Income (loss) before income taxes	65,400,000	54,700,000
Income tax expense (benefit)	22,900,000	18,200,000
Net income (loss)	42,500,000	36,500,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	42,500,000	36,500,000
Preferred stock dividends	(6,000,000)
Net earnings (loss) applicable to common shareholders	36,500,000	36,500,000
Total assets	17,256,000,000	16,167,000,000
Total loans	12,534,000,000	12,829,000,000
Total deposits	14,704,000,000	13,492,000,000
Preferred equity	480,000,000	480,000,000
Common equity	1,386,000,000	1,293,000,000
Noncontrolling interests
Total shareholders' equity	1,866,000,000	1,773,000,000
CB&T [Member]
Segment Reporting Information [Line Items]
Net interest income	117,800,000	128,700,000
Provision for loan losses	(2,900,000)	11,200,000
Net interest income after provision for loan losses	120,700,000	117,500,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent	(9,200,000)	(13,500,000)
Other noninterest income	18,500,000	38,400,000
Noninterest expense	81,200,000	90,300,000
Income (loss) before income taxes	48,800,000	52,100,000
Income tax expense (benefit)	19,100,000	20,500,000
Net income (loss)	29,700,000	31,600,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	29,700,000	31,600,000
Preferred stock dividends	(3,300,000)
Net earnings (loss) applicable to common shareholders	26,400,000	31,600,000
Total assets	10,834,000,000	10,766,000,000
Total loans	8,344,000,000	8,347,000,000
Total deposits	9,113,000,000	9,213,000,000
Preferred equity	262,000,000	262,000,000
Common equity	1,281,000,000	1,190,000,000
Noncontrolling interests
Total shareholders' equity	1,543,000,000	1,452,000,000
Number of branches	102
Amegy [Member]
Segment Reporting Information [Line Items]
Net interest income	94,300,000	93,000,000
Provision for loan losses	(23,300,000)	3,300,000
Net interest income after provision for loan losses	117,600,000	89,700,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent
Other noninterest income	33,600,000	34,000,000
Noninterest expense	82,000,000	79,900,000
Income (loss) before income taxes	69,200,000	43,800,000
Income tax expense (benefit)	23,300,000	14,200,000
Net income (loss)	45,900,000	29,600,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	45,900,000	29,600,000
Preferred stock dividends	(6,100,000)
Net earnings (loss) applicable to common shareholders	39,800,000	29,600,000
Total assets	12,035,000,000	11,221,000,000
Total loans	7,875,000,000	7,571,000,000
Total deposits	9,473,000,000	8,700,000,000
Preferred equity	488,000,000	488,000,000
Common equity	1,645,000,000	1,510,000,000
Noncontrolling interests
Total shareholders' equity	2,133,000,000	1,998,000,000
Number of branches	82
NBA [Member]
Segment Reporting Information [Line Items]
Net interest income	42,100,000	43,100,000
Provision for loan losses	6,500,000	700,000
Net interest income after provision for loan losses	35,600,000	42,400,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent
Other noninterest income	7,700,000	8,500,000
Noninterest expense	37,900,000	45,100,000
Income (loss) before income taxes	5,400,000	5,800,000
Income tax expense (benefit)	2,100,000	2,300,000
Net income (loss)	3,300,000	3,500,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	3,300,000	3,500,000
Preferred stock dividends
Net earnings (loss) applicable to common shareholders	3,300,000	3,500,000
Total assets	4,467,000,000	4,428,000,000
Total loans	3,280,000,000	3,273,000,000
Total deposits	3,709,000,000	3,711,000,000
Preferred equity	305,000,000	305,000,000
Common equity	352,000,000	324,000,000
Noncontrolling interests
Total shareholders' equity	657,000,000	629,000,000
Number of branches	73
NSB [Member]
Segment Reporting Information [Line Items]
Net interest income	31,200,000	33,100,000
Provision for loan losses	(6,700,000)	800,000
Net interest income after provision for loan losses	37,900,000	32,300,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent
Other noninterest income	7,900,000	8,600,000
Noninterest expense	35,300,000	34,600,000
Income (loss) before income taxes	10,500,000	6,300,000
Income tax expense (benefit)	3,600,000	2,100,000
Net income (loss)	6,900,000	4,200,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	6,900,000	4,200,000
Preferred stock dividends
Net earnings (loss) applicable to common shareholders	6,900,000	4,200,000
Total assets	4,125,000,000	4,099,000,000
Total loans	2,203,000,000	2,424,000,000
Total deposits	3,568,000,000	3,488,000,000
Preferred equity	260,000,000	360,000,000
Common equity	275,000,000	227,000,000
Noncontrolling interests
Total shareholders' equity	535,000,000	587,000,000
Number of branches	53
Vectra [Member]
Segment Reporting Information [Line Items]
Net interest income	25,700,000	25,800,000
Provision for loan losses	1,000,000	3,100,000
Net interest income after provision for loan losses	24,700,000	22,700,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent
Other noninterest income	5,400,000	5,500,000
Noninterest expense	24,900,000	24,700,000
Income (loss) before income taxes	5,200,000	3,500,000
Income tax expense (benefit)	1,600,000	1,000,000
Net income (loss)	3,600,000	2,500,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	3,600,000	2,500,000
Preferred stock dividends
Net earnings (loss) applicable to common shareholders	3,600,000	2,500,000
Total assets	2,364,000,000	2,253,000,000
Total loans	1,933,000,000	1,783,000,000
Total deposits	2,027,000,000	1,873,000,000
Preferred equity	70,000,000	70,000,000
Common equity	202,000,000	202,000,000
Noncontrolling interests
Total shareholders' equity	272,000,000	272,000,000
TCBW [Member]
Segment Reporting Information [Line Items]
Net interest income	7,400,000	7,600,000
Provision for loan losses	600,000	1,900,000
Net interest income after provision for loan losses	6,800,000	5,700,000
Net impairment losses on investment securities
Loss on sale of investment securities to Parent
Other noninterest income	600,000	500,000
Noninterest expense	4,700,000	4,500,000
Income (loss) before income taxes	2,700,000	1,700,000
Income tax expense (benefit)	900,000	500,000
Net income (loss)	1,800,000	1,200,000
Net income (loss) applicable to noncontrolling interests
Net income (loss) applicable to controlling interest	1,800,000	1,200,000
Preferred stock dividends
Net earnings (loss) applicable to common shareholders	1,800,000	1,200,000
Total assets	897,000,000	852,000,000
Total loans	555,000,000	568,000,000
Total deposits	747,000,000	669,000,000
Preferred equity	15,000,000	15,000,000
Common equity	76,000,000	70,000,000
Noncontrolling interests
Total shareholders' equity	91,000,000	85,000,000
Number of branches	1
Other Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	(48,800,000)	(80,000,000)
Net interest income after provision for loan losses	(48,800,000)	(80,000,000)
Net impairment losses on investment securities	(10,200,000)	(3,100,000)
Loss on sale of investment securities to Parent	9,200,000	13,500,000
Other noninterest income	(11,800,000)	(7,800,000)
Noninterest expense	4,300,000	900,000
Income (loss) before income taxes	(65,900,000)	(78,300,000)
Income tax expense (benefit)	(21,600,000)	(21,800,000)
Net income (loss)	(44,300,000)	(56,500,000)
Net income (loss) applicable to noncontrolling interests	(300,000)	(200,000)
Net income (loss) applicable to controlling interest	(44,000,000)	(56,300,000)
Preferred stock dividends	(48,800,000)	(38,000,000)
Net earnings (loss) applicable to common shareholders	(92,800,000)	(94,300,000)
Total assets	602,000,000	919,000,000
Total loans	68,000,000	(127,000,000)
Total deposits	(970,000,000)	(557,000,000)
Preferred equity	475,000,000	97,000,000
Common equity	(572,000,000)	(173,000,000)
Noncontrolling interests	(2,000,000)	(1,000,000)
Total shareholders' equity	(99,000,000)	(77,000,000)
Consolidated Company [Member]
Segment Reporting Information [Line Items]
Net interest income	442,300,000	423,900,000
Provision for loan losses	15,700,000	60,000,000
Net interest income after provision for loan losses	426,600,000	363,900,000
Net impairment losses on investment securities	(10,200,000)	(3,100,000)
Loss on sale of investment securities to Parent
Other noninterest income	117,200,000	137,200,000
Noninterest expense	392,300,000	408,400,000
Income (loss) before income taxes	141,300,000	89,600,000
Income tax expense (benefit)	51,900,000	37,000,000
Net income (loss)	89,400,000	52,600,000
Net income (loss) applicable to noncontrolling interests	(300,000)	(200,000)
Net income (loss) applicable to controlling interest	89,700,000	52,800,000
Preferred stock dividends	(64,200,000)	(38,000,000)
Net earnings (loss) applicable to common shareholders	25,500,000	14,800,000
Total assets	52,580,000,000	50,705,000,000
Total loans	36,792,000,000	36,668,000,000
Total deposits	42,371,000,000	40,589,000,000
Preferred equity	2,355,000,000	2,077,000,000
Common equity	4,645,000,000	4,643,000,000
Noncontrolling interests	(2,000,000)	(1,000,000)
Total shareholders' equity	$ 6,998,000,000	$ 6,719,000,000
TCBO [Member]
Segment Reporting Information [Line Items]
Number of branches	1
Utah [Member] | Zions Bank [Member]
Segment Reporting Information [Line Items]
Number of branches	105
Idaho [Member] | Zions Bank [Member]
Segment Reporting Information [Line Items]
Number of branches	27
Colorado [Member] | Vectra [Member]
Segment Reporting Information [Line Items]
Number of branches	38
New Mexico [Member] | Vectra [Member]
Segment Reporting Information [Line Items]
Number of branches	1