Operating Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012 Banks	Sep. 30, 2011	Sep. 30, 2012 Banks	Sep. 30, 2011
Segment Reporting Information [Line Items]
Net interest income	$ 444,198,000	$ 470,595,000	$ 1,318,484,000	$ 1,310,623,000
Provision for loan losses	(1,889,000)	14,553,000	24,628,000	75,883,000
Net interest income after provision for loan losses	446,087,000	456,042,000	1,293,856,000	1,234,740,000
Net impairment losses on investment securities	(2,736,000)	(13,334,000)	(20,253,000)	(21,597,000)
Other noninterest income	3,495,000	2,789,000	9,820,000	27,651,000
Noninterest expense	394,975,000	409,018,000	1,189,003,000	1,233,649,000
Income (loss) before income taxes	170,301,000	168,066,000	454,063,000	384,625,000
Income tax expense (benefit)	60,704,000	59,348,000	163,599,000	150,706,000
Net income	109,597,000	108,718,000	290,464,000	233,919,000
Net income (loss) applicable to noncontrolling interests	(254,000)	(375,000)	(800,000)	(866,000)
Net income (loss) applicable to controlling interest	109,851,000	109,093,000	291,264,000	234,785,000
Preferred stock dividends			(103,542,000)	(109,723,000)
Net earnings (loss) applicable to common shareholders	62,322,000	65,165,000	143,026,000	108,970,000
Number of community/regional banks operating in distinct geographical areas	8		8
Zions Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	170,600,000	177,600,000	514,800,000	526,600,000
Provision for loan losses	17,100,000	30,500,000	78,000,000	91,100,000
Net interest income after provision for loan losses	153,500,000	147,100,000	436,800,000	435,500,000
Net impairment losses on investment securities	(100,000)	(300,000)	(300,000)	(300,000)
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	46,500,000	55,700,000	147,400,000	154,800,000
Noninterest expense	123,500,000	142,200,000	371,000,000	407,800,000
Income (loss) before income taxes	76,400,000	60,300,000	212,900,000	182,200,000
Income tax expense (benefit)	27,400,000	20,500,000	75,500,000	61,700,000
Net income	49,000,000	39,800,000	137,400,000	120,500,000
Total assets	17,641,000,000	16,259,000,000	17,410,000,000	16,192,000,000
Average cash and due from banks	359,000,000	361,000,000	367,000,000	379,000,000
Average money market investments	2,725,000,000	1,071,000,000	2,507,000,000	807,000,000
Average Securities	1,331,000,000	1,496,000,000	1,380,000,000	1,573,000,000
Total loans	12,566,000,000	12,686,000,000	12,501,000,000	12,771,000,000
Total deposits	15,140,000,000	13,741,000,000	14,887,000,000	13,619,000,000
Preferred equity	444,000,000	480,000,000	468,000,000	480,000,000
Common equity	1,441,000,000	1,351,000,000	1,419,000,000	1,310,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	1,885,000,000	1,831,000,000	1,887,000,000	1,790,000,000
CB&T [Member]
Segment Reporting Information [Line Items]
Net interest income	118,700,000	127,800,000	354,400,000	384,900,000
Provision for loan losses	(2,800,000)	(1,500,000)	(9,500,000)	3,900,000
Net interest income after provision for loan losses	121,500,000	129,300,000	363,900,000	381,000,000
Net impairment losses on investment securities	0	(500,000)	0	(500,000)
Loss on sale of investment securities to Parent	0	(7,200,000)	(9,200,000)	(20,700,000)
Other noninterest income	18,600,000	22,100,000	55,500,000	84,300,000
Noninterest expense	85,200,000	89,300,000	250,800,000	272,700,000
Income (loss) before income taxes	54,900,000	54,400,000	159,400,000	171,400,000
Income tax expense (benefit)	21,800,000	21,400,000	63,100,000	67,900,000
Net income	33,100,000	33,000,000	96,300,000	103,500,000
Total assets	11,000,000,000	10,960,000,000	10,905,000,000	10,844,000,000
Average cash and due from banks	168,000,000	179,000,000	176,000,000	187,000,000
Average money market investments	1,296,000,000	1,254,000,000	1,175,000,000	1,065,000,000
Average Securities	362,000,000	391,000,000	350,000,000	399,000,000
Total loans	8,332,000,000	8,257,000,000	8,342,000,000	8,296,000,000
Total deposits	9,404,000,000	9,336,000,000	9,246,000,000	9,257,000,000
Preferred equity	184,000,000	262,000,000	231,000,000	262,000,000
Common equity	1,307,000,000	1,260,000,000	1,293,000,000	1,225,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	1,491,000,000	1,522,000,000	1,524,000,000	1,487,000,000
Number of branches	102		102
Amegy [Member]
Segment Reporting Information [Line Items]
Net interest income	91,000,000	99,400,000	275,700,000	290,700,000
Provision for loan losses	(18,300,000)	(13,000,000)	(50,500,000)	(9,900,000)
Net interest income after provision for loan losses	109,300,000	112,400,000	326,200,000	300,600,000
Net impairment losses on investment securities	0	0	0	0
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	38,900,000	37,800,000	117,800,000	111,100,000
Noninterest expense	86,300,000	74,300,000	255,100,000	238,300,000
Income (loss) before income taxes	61,900,000	75,900,000	188,900,000	173,400,000
Income tax expense (benefit)	20,800,000	25,600,000	62,900,000	57,500,000
Net income	41,100,000	50,300,000	126,000,000	115,900,000
Total assets	12,231,000,000	11,362,000,000	12,116,000,000	11,273,000,000
Average cash and due from banks	259,000,000	284,000,000	293,000,000	298,000,000
Average money market investments	2,446,000,000	1,575,000,000	2,357,000,000	1,545,000,000
Average Securities	315,000,000	420,000,000	331,000,000	451,000,000
Total loans	7,981,000,000	7,858,000,000	7,922,000,000	7,742,000,000
Total deposits	9,805,000,000	8,831,000,000	9,625,000,000	8,748,000,000
Preferred equity	330,000,000	488,000,000	409,000,000	488,000,000
Common equity	1,689,000,000	1,580,000,000	1,665,000,000	1,545,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	2,019,000,000	2,068,000,000	2,074,000,000	2,033,000,000
Number of branches	82		82
NBA [Member]
Segment Reporting Information [Line Items]
Net interest income	42,100,000	43,000,000	125,600,000	129,400,000
Provision for loan losses	1,800,000	7,600,000	10,800,000	10,100,000
Net interest income after provision for loan losses	40,300,000	35,400,000	114,800,000	119,300,000
Net impairment losses on investment securities	0	0	0	0
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	7,500,000	8,800,000	23,000,000	26,800,000
Noninterest expense	37,300,000	36,300,000	113,200,000	118,400,000
Income (loss) before income taxes	10,500,000	7,900,000	24,600,000	27,700,000
Income tax expense (benefit)	3,400,000	3,100,000	8,900,000	10,900,000
Net income	7,100,000	4,800,000	15,700,000	16,800,000
Total assets	4,447,000,000	4,458,000,000	4,457,000,000	4,456,000,000
Average cash and due from banks	70,000,000	65,000,000	70,000,000	65,000,000
Average money market investments	482,000,000	605,000,000	569,000,000	611,000,000
Average Securities	274,000,000	273,000,000	276,000,000	255,000,000
Total loans	3,402,000,000	3,277,000,000	3,321,000,000	3,285,000,000
Total deposits	3,766,000,000	3,722,000,000	3,732,000,000	3,726,000,000
Preferred equity	198,000,000	305,000,000	259,000,000	305,000,000
Common equity	379,000,000	337,000,000	363,000,000	331,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	577,000,000	642,000,000	622,000,000	636,000,000
Number of branches	74		74
NSB [Member]
Segment Reporting Information [Line Items]
Net interest income	30,400,000	33,500,000	92,600,000	101,900,000
Provision for loan losses	(1,200,000)	(15,600,000)	(9,500,000)	(33,000,000)
Net interest income after provision for loan losses	31,600,000	49,100,000	102,100,000	134,900,000
Net impairment losses on investment securities	0	0	0	0
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	8,800,000	9,800,000	25,200,000	28,500,000
Noninterest expense	31,300,000	35,400,000	100,900,000	105,700,000
Income (loss) before income taxes	9,100,000	23,500,000	26,400,000	57,700,000
Income tax expense (benefit)	3,100,000	8,100,000	9,100,000	20,000,000
Net income	6,000,000	15,400,000	17,300,000	37,700,000
Total assets	4,085,000,000	4,232,000,000	4,127,000,000	4,167,000,000
Average cash and due from banks	83,000,000	93,000,000	87,000,000	85,000,000
Average money market investments	936,000,000	961,000,000	960,000,000	924,000,000
Average Securities	774,000,000	689,000,000	770,000,000	646,000,000
Total loans	2,156,000,000	2,360,000,000	2,176,000,000	2,397,000,000
Total deposits	3,597,000,000	3,595,000,000	3,597,000,000	3,544,000,000
Preferred equity	180,000,000	360,000,000	227,000,000	360,000,000
Common equity	286,000,000	252,000,000	280,000,000	238,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	466,000,000	612,000,000	507,000,000	598,000,000
Number of branches	53		53
Vectra [Member]
Segment Reporting Information [Line Items]
Net interest income	27,400,000	26,500,000	81,700,000	78,300,000
Provision for loan losses	2,200,000	5,300,000	4,600,000	7,200,000
Net interest income after provision for loan losses	25,200,000	21,200,000	77,100,000	71,100,000
Net impairment losses on investment securities	0	(500,000)	0	(500,000)
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	7,500,000	5,700,000	18,500,000	16,500,000
Noninterest expense	23,400,000	23,700,000	73,000,000	74,700,000
Income (loss) before income taxes	9,300,000	2,700,000	22,600,000	12,400,000
Income tax expense (benefit)	3,200,000	700,000	7,500,000	3,800,000
Net income	6,100,000	2,000,000	15,100,000	8,600,000
Total assets	2,441,000,000	2,273,000,000	2,395,000,000	2,257,000,000
Average cash and due from banks	54,000,000	49,000,000	52,000,000	51,000,000
Average money market investments	47,000,000	28,000,000	49,000,000	67,000,000
Average Securities	207,000,000	259,000,000	217,000,000	257,000,000
Total loans	2,046,000,000	1,864,000,000	1,991,000,000	1,813,000,000
Total deposits	2,085,000,000	1,906,000,000	2,047,000,000	1,884,000,000
Preferred equity	70,000,000	70,000,000	70,000,000	70,000,000
Common equity	214,000,000	206,000,000	208,000,000	204,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	284,000,000	276,000,000	278,000,000	274,000,000
TCBW [Member]
Segment Reporting Information [Line Items]
Net interest income	7,100,000	7,600,000	21,600,000	22,800,000
Provision for loan losses	(700,000)	1,300,000	700,000	6,400,000
Net interest income after provision for loan losses	7,800,000	6,300,000	20,900,000	16,400,000
Net impairment losses on investment securities	0	0	0	0
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	800,000	800,000	2,100,000	2,100,000
Noninterest expense	4,900,000	4,300,000	13,900,000	12,700,000
Income (loss) before income taxes	3,700,000	2,800,000	9,100,000	5,800,000
Income tax expense (benefit)	1,300,000	1,000,000	3,100,000	1,900,000
Net income	2,400,000	1,800,000	6,000,000	3,900,000
Total assets	863,000,000	891,000,000	877,000,000	865,000,000
Average cash and due from banks	20,000,000	18,000,000	20,000,000	18,000,000
Average money market investments	158,000,000	142,000,000	168,000,000	116,000,000
Average Securities	115,000,000	134,000,000	119,000,000	138,000,000
Total loans	556,000,000	583,000,000	556,000,000	579,000,000
Total deposits	722,000,000	700,000,000	730,000,000	680,000,000
Preferred equity	2,000,000	15,000,000	10,000,000	15,000,000
Common equity	80,000,000	74,000,000	78,000,000	72,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	82,000,000	89,000,000	88,000,000	87,000,000
Number of branches	1		1
Other Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	(43,100,000)	(44,800,000)	(147,900,000)	(224,000,000)
Provision for loan losses	0	0	0	100,000
Net interest income after provision for loan losses	(43,100,000)	(44,800,000)	(147,900,000)	(224,100,000)
Net impairment losses on investment securities	(2,600,000)	(12,000,000)	(20,000,000)	(20,300,000)
Loss on sale of investment securities to Parent	0	7,200,000	9,200,000	20,700,000
Other noninterest income	(6,700,000)	(6,300,000)	(20,000,000)	(19,000,000)
Noninterest expense	3,100,000	3,500,000	11,100,000	3,300,000
Income (loss) before income taxes	(55,500,000)	(59,400,000)	(189,800,000)	(246,000,000)
Income tax expense (benefit)	(20,300,000)	(21,000,000)	(66,500,000)	(73,000,000)
Net income	(35,200,000)	(38,400,000)	(123,300,000)	(173,000,000)
Total assets	659,000,000	1,139,000,000	660,000,000	1,039,000,000
Average cash and due from banks	(13,000,000)	(13,000,000)	(16,000,000)	(33,000,000)
Average money market investments	(100,000,000)	(117,000,000)	(98,000,000)	(189,000,000)
Average Securities	447,000,000	1,166,000,000	444,000,000	1,191,000,000
Total loans	70,000,000	(101,000,000)	68,000,000	(119,000,000)
Total deposits	(1,041,000,000)	(434,000,000)	(932,000,000)	(498,000,000)
Preferred equity	357,000,000	355,000,000	309,000,000	240,000,000
Common equity	(637,000,000)	(426,000,000)	(600,000,000)	(300,000,000)
Noncontrolling interests	(3,000,000)	(2,000,000)	(3,000,000)	(1,000,000)
Total shareholders' equity	(283,000,000)	(73,000,000)	(294,000,000)	(61,000,000)
Consolidated Company [Member]
Segment Reporting Information [Line Items]
Net interest income	444,200,000	470,600,000	1,318,500,000	1,310,600,000
Provision for loan losses	(1,900,000)	14,600,000	24,600,000	75,900,000
Net interest income after provision for loan losses	446,100,000	456,000,000	1,293,900,000	1,234,700,000
Net impairment losses on investment securities	(2,700,000)	(13,300,000)	(20,300,000)	(21,600,000)
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	121,900,000	134,400,000	369,500,000	405,100,000
Noninterest expense	395,000,000	409,000,000	1,189,000,000	1,233,600,000
Income (loss) before income taxes	170,300,000	168,100,000	454,100,000	384,600,000
Income tax expense (benefit)	60,700,000	59,400,000	163,600,000	150,700,000
Net income	109,600,000	108,700,000	290,500,000	233,900,000
Total assets	53,367,000,000	51,574,000,000	52,947,000,000	51,093,000,000
Average cash and due from banks	1,000,000,000	1,036,000,000	1,049,000,000	1,050,000,000
Average money market investments	7,990,000,000	5,519,000,000	7,687,000,000	4,946,000,000
Average Securities	3,825,000,000	4,828,000,000	3,887,000,000	4,910,000,000
Total loans	37,109,000,000	36,784,000,000	36,877,000,000	36,764,000,000
Total deposits	43,478,000,000	41,397,000,000	42,932,000,000	40,960,000,000
Preferred equity	1,765,000,000	2,335,000,000	1,983,000,000	2,220,000,000
Common equity	4,759,000,000	4,634,000,000	4,706,000,000	4,625,000,000
Noncontrolling interests	(3,000,000)	(2,000,000)	(3,000,000)	(1,000,000)
Total shareholders' equity	$ 6,521,000,000	$ 6,967,000,000	$ 6,686,000,000	$ 6,844,000,000
TCBO [Member]
Segment Reporting Information [Line Items]
Number of branches	1		1
Utah [Member] | Zions Bank [Member]
Segment Reporting Information [Line Items]
Number of branches	105		105
Idaho [Member] | Zions Bank [Member]
Segment Reporting Information [Line Items]
Number of branches	26		26
Colorado [Member] | Vectra [Member]
Segment Reporting Information [Line Items]
Number of branches	38		38
New Mexico [Member] | Vectra [Member]
Segment Reporting Information [Line Items]
Number of branches	1		1