Operating Segment Information (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 Banks	Sep. 30, 2012	Sep. 30, 2013 Banks	Sep. 30, 2012
Segment Reporting Information [Line Items]
Net interest income	$ 415,521,000	$ 438,161,000	$ 1,264,293,000	$ 1,301,983,000
Provision for loan losses	(5,573,000)	(1,889,000)	(56,598,000)	24,628,000
Net interest income after provision for loan losses	421,094,000	440,050,000	1,320,891,000	1,277,355,000
Net impairment losses on investment securities	10,470,000	3,876,000	46,873,000	46,175,000
Other noninterest income	5,243,000	3,495,000	15,942,000	9,820,000
Noninterest expense	370,663,000	394,975,000	1,219,689,000	1,189,003,000
Income before income taxes	172,621,000	170,301,000	469,759,000	454,063,000
Income Tax Expense (Benefit)	61,107,000	60,704,000	164,832,000	163,599,000
Net income	111,514,000	109,597,000	304,927,000	290,464,000
Number of community/regional banks operating in distinct geographical areas	8		8
Zions Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	145,100,000	165,000,000	447,400,000	498,700,000
Provision for loan losses	(9,500,000)	17,100,000	(18,400,000)	78,000,000
Net interest income after provision for loan losses	154,600,000	147,900,000	465,800,000	420,700,000
Net impairment losses on investment securities	0	(100,000)	0	(300,000)
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	47,700,000	52,100,000	152,200,000	163,500,000
Noninterest expense	119,100,000	123,500,000	362,100,000	371,000,000
Income before income taxes	83,200,000	76,400,000	255,900,000	212,900,000
Income Tax Expense (Benefit)	30,200,000	27,400,000	93,300,000	75,500,000
Net income	53,000,000	49,000,000	162,600,000	137,400,000
Total assets	18,237,000,000	17,641,000,000	17,609,000,000	17,410,000,000
Average cash and due from banks	339,000,000	359,000,000	347,000,000	367,000,000
Average money market investments	3,868,000,000	2,725,000,000	3,113,000,000	2,507,000,000
Average Securities	1,287,000,000	1,331,000,000	1,279,000,000	1,380,000,000
Total loans	12,271,000,000	12,566,000,000	12,330,000,000	12,501,000,000
Total deposits	15,951,000,000	15,140,000,000	15,314,000,000	14,887,000,000
Preferred equity	280,000,000	444,000,000	280,000,000	468,000,000
Common equity	1,530,000,000	1,441,000,000	1,524,000,000	1,419,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	1,810,000,000	1,885,000,000	1,804,000,000	1,887,000,000
CB&T [Member]
Segment Reporting Information [Line Items]
Net interest income	109,800,000	118,000,000	347,000,000	352,400,000
Provision for loan losses	(3,000,000)	(2,800,000)	(12,800,000)	(9,500,000)
Net interest income after provision for loan losses	112,800,000	120,800,000	359,800,000	361,900,000
Net impairment losses on investment securities	0	0	0	0
Loss on sale of investment securities to Parent	0	0	0	(9,200,000)
Other noninterest income	20,800,000	19,300,000	62,100,000	57,500,000
Noninterest expense	75,900,000	85,200,000	260,700,000	250,800,000
Income before income taxes	57,700,000	54,900,000	161,200,000	159,400,000
Income Tax Expense (Benefit)	23,000,000	21,800,000	63,700,000	63,100,000
Net income	34,700,000	33,100,000	97,500,000	96,300,000
Total assets	10,869,000,000	11,000,000,000	10,871,000,000	10,905,000,000
Average cash and due from banks	164,000,000	168,000,000	168,000,000	176,000,000
Average money market investments	1,288,000,000	1,296,000,000	1,284,000,000	1,175,000,000
Average Securities	321,000,000	362,000,000	333,000,000	350,000,000
Total loans	8,328,000,000	8,332,000,000	8,297,000,000	8,342,000,000
Total deposits	9,261,000,000	9,404,000,000	9,267,000,000	9,246,000,000
Preferred equity	162,000,000	184,000,000	162,000,000	231,000,000
Common equity	1,326,000,000	1,307,000,000	1,324,000,000	1,293,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	1,488,000,000	1,491,000,000	1,486,000,000	1,524,000,000
Number of branches	97		97
Amegy [Member]
Segment Reporting Information [Line Items]
Net interest income	95,500,000	91,600,000	284,900,000	278,500,000
Provision for loan losses	12,800,000	(18,300,000)	4,700,000	(50,500,000)
Net interest income after provision for loan losses	82,700,000	109,900,000	280,200,000	329,000,000
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	37,100,000	38,300,000	111,000,000	115,000,000
Noninterest expense	75,300,000	86,300,000	251,400,000	255,100,000
Income before income taxes	44,500,000	61,900,000	139,800,000	188,900,000
Income Tax Expense (Benefit)	14,900,000	20,800,000	46,800,000	62,900,000
Net income	29,600,000	41,100,000	93,000,000	126,000,000
Total assets	13,453,000,000	12,231,000,000	13,122,000,000	12,116,000,000
Average cash and due from banks	255,000,000	259,000,000	283,000,000	293,000,000
Average money market investments	2,823,000,000	2,446,000,000	2,563,000,000	2,357,000,000
Average Securities	285,000,000	313,000,000	336,000,000	331,000,000
Total loans	8,981,000,000	8,073,000,000	8,790,000,000	8,012,000,000
Total deposits	11,024,000,000	9,805,000,000	10,707,000,000	9,625,000,000
Preferred equity	248,000,000	330,000,000	250,000,000	409,000,000
Common equity	1,805,000,000	1,689,000,000	1,775,000,000	1,665,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	2,053,000,000	2,019,000,000	2,025,000,000	2,074,000,000
Number of branches	84		84
NBA [Member]
Segment Reporting Information [Line Items]
Net interest income	40,500,000	41,900,000	122,400,000	125,300,000
Provision for loan losses	(7,300,000)	1,700,000	(12,000,000)	10,700,000
Net interest income after provision for loan losses	47,800,000	40,200,000	134,400,000	114,600,000
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	8,600,000	7,600,000	25,600,000	23,200,000
Noninterest expense	35,300,000	37,300,000	104,900,000	113,200,000
Income before income taxes	21,100,000	10,500,000	55,100,000	24,600,000
Income Tax Expense (Benefit)	7,700,000	3,400,000	20,500,000	8,900,000
Net income	13,400,000	7,100,000	34,600,000	15,700,000
Total assets	4,624,000,000	4,447,000,000	4,612,000,000	4,457,000,000
Average cash and due from banks	70,000,000	70,000,000	70,000,000	70,000,000
Average money market investments	444,000,000	482,000,000	452,000,000	569,000,000
Average Securities	320,000,000	274,000,000	298,000,000	276,000,000
Total loans	3,600,000,000	3,402,000,000	3,588,000,000	3,321,000,000
Total deposits	3,945,000,000	3,766,000,000	3,919,000,000	3,732,000,000
Preferred equity	153,000,000	198,000,000	171,000,000	259,000,000
Common equity	410,000,000	379,000,000	406,000,000	363,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	563,000,000	577,000,000	577,000,000	622,000,000
Number of branches	72		72
NSB [Member]
Segment Reporting Information [Line Items]
Net interest income	28,400,000	30,400,000	84,400,000	92,600,000
Provision for loan losses	0	(1,200,000)	(8,900,000)	(9,500,000)
Net interest income after provision for loan losses	28,400,000	31,600,000	93,300,000	102,100,000
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	11,400,000	8,800,000	30,000,000	25,300,000
Noninterest expense	32,000,000	31,300,000	97,900,000	101,000,000
Income before income taxes	7,800,000	9,100,000	25,400,000	26,400,000
Income Tax Expense (Benefit)	2,600,000	3,100,000	8,600,000	9,100,000
Net income	5,200,000	6,000,000	16,800,000	17,300,000
Total assets	4,022,000,000	4,085,000,000	4,046,000,000	4,127,000,000
Average cash and due from banks	87,000,000	83,000,000	85,000,000	87,000,000
Average money market investments	883,000,000	936,000,000	944,000,000	960,000,000
Average Securities	785,000,000	774,000,000	769,000,000	770,000,000
Total loans	2,158,000,000	2,156,000,000	2,127,000,000	2,176,000,000
Total deposits	3,600,000,000	3,597,000,000	3,606,000,000	3,597,000,000
Preferred equity	90,000,000	180,000,000	114,000,000	227,000,000
Common equity	310,000,000	286,000,000	304,000,000	280,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	400,000,000	466,000,000	418,000,000	507,000,000
Number of branches	51		51
Vectra [Member]
Segment Reporting Information [Line Items]
Net interest income	25,800,000	27,300,000	76,500,000	81,500,000
Provision for loan losses	1,800,000	2,200,000	(7,600,000)	4,600,000
Net interest income after provision for loan losses	24,000,000	25,100,000	84,100,000	76,900,000
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	6,500,000	7,600,000	19,600,000	18,700,000
Noninterest expense	24,400,000	23,400,000	75,000,000	73,000,000
Income before income taxes	6,100,000	9,300,000	28,700,000	22,600,000
Income Tax Expense (Benefit)	2,100,000	3,200,000	10,000,000	7,500,000
Net income	4,000,000	6,100,000	18,700,000	15,100,000
Total assets	2,630,000,000	2,441,000,000	2,541,000,000	2,395,000,000
Average cash and due from banks	48,000,000	54,000,000	50,000,000	52,000,000
Average money market investments	127,000,000	47,000,000	84,000,000	49,000,000
Average Securities	184,000,000	207,000,000	184,000,000	217,000,000
Total loans	2,195,000,000	2,046,000,000	2,142,000,000	1,991,000,000
Total deposits	2,258,000,000	2,085,000,000	2,177,000,000	2,047,000,000
Preferred equity	70,000,000	70,000,000	70,000,000	70,000,000
Common equity	241,000,000	214,000,000	235,000,000	208,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	311,000,000	284,000,000	305,000,000	278,000,000
TCBW [Member]
Segment Reporting Information [Line Items]
Net interest income	7,000,000	6,900,000	20,300,000	20,900,000
Provision for loan losses	(300,000)	(600,000)	(1,100,000)	800,000
Net interest income after provision for loan losses	7,300,000	7,500,000	21,400,000	20,100,000
Net impairment losses on investment securities	0	0	0	0
Loss on sale of investment securities to Parent	(2,700,000)	0	(2,700,000)	0
Other noninterest income	1,000,000	1,000,000	3,000,000	2,800,000
Noninterest expense	4,800,000	4,900,000	13,600,000	13,900,000
Income before income taxes	800,000	3,600,000	8,100,000	9,000,000
Income Tax Expense (Benefit)	300,000	1,200,000	2,800,000	3,000,000
Net income	500,000	2,400,000	5,300,000	6,000,000
Total assets	882,000,000	863,000,000	866,000,000	877,000,000
Average cash and due from banks	19,000,000	20,000,000	19,000,000	20,000,000
Average money market investments	121,000,000	158,000,000	135,000,000	168,000,000
Average Securities	101,000,000	115,000,000	103,000,000	119,000,000
Total loans	627,000,000	556,000,000	596,000,000	556,000,000
Total deposits	743,000,000	722,000,000	727,000,000	730,000,000
Preferred equity	3,000,000	2,000,000	3,000,000	10,000,000
Common equity	86,000,000	80,000,000	84,000,000	78,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	89,000,000	82,000,000	87,000,000	88,000,000
Number of branches	1		1
Other Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	(36,600,000)	(42,900,000)	(118,600,000)	(147,900,000)
Provision for loan losses	(100,000)	0	(500,000)	0
Net interest income after provision for loan losses	(36,500,000)	(42,900,000)	(118,100,000)	(147,900,000)
Net impairment losses on investment securities	(9,100,000)	(2,700,000)	(23,400,000)	(20,000,000)
Loss on sale of investment securities to Parent	2,700,000	0	2,700,000	9,200,000
Other noninterest income	(1,800,000)	(6,700,000)	(11,600,000)	(20,000,000)
Noninterest expense	3,900,000	3,100,000	54,100,000	11,000,000
Income before income taxes	(48,600,000)	(55,400,000)	(204,500,000)	(189,700,000)
Income Tax Expense (Benefit)	(19,700,000)	(20,200,000)	(80,900,000)	(66,400,000)
Net income	(28,900,000)	(35,200,000)	(123,600,000)	(123,300,000)
Total assets	798,000,000	659,000,000	1,019,000,000	660,000,000
Average cash and due from banks	(6,000,000)	(13,000,000)	(9,000,000)	(16,000,000)
Average money market investments	(100,000,000)	(100,000,000)	169,000,000	(98,000,000)
Average Securities	592,000,000	449,000,000	551,000,000	444,000,000
Total loans	64,000,000	68,000,000	63,000,000	68,000,000
Total deposits	(1,194,000,000)	(1,041,000,000)	(718,000,000)	(932,000,000)
Preferred equity	680,000,000	357,000,000	429,000,000	309,000,000
Common equity	(518,000,000)	(637,000,000)	(557,000,000)	(600,000,000)
Noncontrolling interests	0	(3,000,000)	(2,000,000)	(3,000,000)
Total shareholders' equity	162,000,000	(283,000,000)	(130,000,000)	(294,000,000)
Consolidated Company [Member]
Segment Reporting Information [Line Items]
Net interest income	415,500,000	438,200,000	1,264,300,000	1,302,000,000
Provision for loan losses	(5,600,000)	(1,900,000)	(56,600,000)	24,600,000
Net interest income after provision for loan losses	421,100,000	440,100,000	1,320,900,000	1,277,400,000
Net impairment losses on investment securities	(9,100,000)	(2,800,000)	(23,400,000)	(20,300,000)
Loss on sale of investment securities to Parent	0	0	0	0
Other noninterest income	131,300,000	128,000,000	391,900,000	386,000,000
Noninterest expense	370,700,000	395,000,000	1,219,700,000	1,189,000,000
Income before income taxes	172,600,000	170,300,000	469,700,000	454,100,000
Income Tax Expense (Benefit)	61,100,000	60,700,000	164,800,000	163,600,000
Net income	111,500,000	109,600,000	304,900,000	290,500,000
Total assets	55,515,000,000	53,367,000,000	54,686,000,000	52,947,000,000
Average cash and due from banks	976,000,000	1,000,000,000	1,013,000,000	1,049,000,000
Average money market investments	9,454,000,000	7,990,000,000	8,744,000,000	7,687,000,000
Average Securities	3,875,000,000	3,825,000,000	3,853,000,000	3,887,000,000
Total loans	38,224,000,000	37,199,000,000	37,933,000,000	36,967,000,000
Total deposits	45,588,000,000	43,478,000,000	44,999,000,000	42,932,000,000
Preferred equity	1,686,000,000	1,765,000,000	1,479,000,000	1,983,000,000
Common equity	5,190,000,000	4,759,000,000	5,095,000,000	4,706,000,000
Noncontrolling interests	0	(3,000,000)	(2,000,000)	(3,000,000)
Total shareholders' equity	$ 6,876,000,000	$ 6,521,000,000	$ 6,572,000,000	$ 6,686,000,000
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	100		100
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