Operating Segment Information (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014 Banks	Jun. 30, 2013	Jun. 30, 2014 Banks	Jun. 30, 2013
Segment Reporting Information [Line Items]
Net interest income	$ 416,283,000	$ 430,657,000	$ 832,748,000	$ 848,772,000
Provision for loan losses	(54,416,000)	(21,990,000)	(55,026,000)	(51,025,000)
Net interest income after provision for loan losses	470,699,000	452,647,000	887,774,000	899,797,000
Net impairment losses on investment securities	0	4,910,000	27,000	36,403,000
Other noninterest income	707,000	4,515,000	3,238,000	10,699,000
Noninterest expense	406,027,000	451,678,000	804,090,000	849,026,000
Income before income taxes	189,522,000	126,117,000	346,853,000	297,138,000
Income Tax Expense (Benefit)	69,972,000	43,091,000	126,093,000	103,725,000
Net income	119,550,000	83,026,000	220,760,000	193,413,000
Number of community/regional banks operating in distinct geographical areas	8		8
Zions Bank [Member]
Segment Reporting Information [Line Items]
Net interest income	145,600,000	150,800,000	288,100,000	302,300,000
Provision for loan losses	(15,400,000)	(10,700,000)	(24,100,000)	(8,900,000)
Net interest income after provision for loan losses	161,000,000	161,500,000	312,200,000	311,200,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	50,200,000	54,200,000	94,200,000	104,500,000
Noninterest expense	121,100,000	128,000,000	242,600,000	243,000,000
Income before income taxes	90,100,000	87,700,000	163,800,000	172,700,000
Income Tax Expense (Benefit)	33,200,000	32,100,000	60,000,000	63,100,000
Net income	56,900,000	55,600,000	103,800,000	109,600,000
Total assets	17,593,000,000	17,522,000,000	17,932,000,000	17,290,000,000
Average cash and due from banks	336,000,000	352,000,000	338,000,000	351,000,000
Average money market investments	2,678,000,000	2,949,000,000	3,109,000,000	2,729,000,000
Average Securities	1,747,000,000	1,311,000,000	1,672,000,000	1,275,000,000
Total loans	12,317,000,000	12,363,000,000	12,282,000,000	12,360,000,000
Total deposits	15,320,000,000	15,234,000,000	15,648,000,000	14,990,000,000
Preferred equity	280,000,000	280,000,000	280,000,000	280,000,000
Common equity	1,552,000,000	1,533,000,000	1,545,000,000	1,521,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	1,832,000,000	1,813,000,000	1,825,000,000	1,801,000,000
CB&T [Member]
Segment Reporting Information [Line Items]
Net interest income	103,700,000	122,600,000	212,900,000	237,200,000
Provision for loan losses	(12,900,000)	(3,000,000)	(15,000,000)	(9,800,000)
Net interest income after provision for loan losses	116,600,000	125,600,000	227,900,000	247,000,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	13,800,000	19,700,000	19,600,000	41,300,000
Noninterest expense	82,400,000	94,500,000	167,700,000	184,800,000
Income before income taxes	48,000,000	50,800,000	79,800,000	103,500,000
Income Tax Expense (Benefit)	19,000,000	19,900,000	31,100,000	40,700,000
Net income	29,000,000	30,900,000	48,700,000	62,800,000
Total assets	11,044,000,000	10,823,000,000	10,967,000,000	10,872,000,000
Average cash and due from banks	156,000,000	165,000,000	161,000,000	170,000,000
Average money market investments	1,252,000,000	1,237,000,000	1,191,000,000	1,282,000,000
Average Securities	237,000,000	334,000,000	282,000,000	339,000,000
Total loans	8,655,000,000	8,287,000,000	8,597,000,000	8,281,000,000
Total deposits	9,395,000,000	9,231,000,000	9,334,000,000	9,270,000,000
Preferred equity	162,000,000	162,000,000	162,000,000	162,000,000
Common equity	1,368,000,000	1,319,000,000	1,359,000,000	1,323,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	1,530,000,000	1,481,000,000	1,521,000,000	1,485,000,000
Number of branches	95		95
Amegy [Member]
Segment Reporting Information [Line Items]
Net interest income	95,400,000	94,000,000	190,100,000	189,400,000
Provision for loan losses	(7,500,000)	5,700,000	9,400,000	(8,100,000)
Net interest income after provision for loan losses	102,900,000	88,300,000	180,700,000	197,500,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	36,300,000	35,500,000	68,300,000	73,900,000
Noninterest expense	92,500,000	91,900,000	179,500,000	176,100,000
Income before income taxes	46,700,000	31,900,000	69,500,000	95,300,000
Income Tax Expense (Benefit)	15,900,000	10,600,000	23,200,000	31,900,000
Net income	30,800,000	21,300,000	46,300,000	63,400,000
Total assets	13,618,000,000	13,215,000,000	13,543,000,000	12,954,000,000
Average cash and due from banks	213,000,000	273,000,000	267,000,000	297,000,000
Average money market investments	2,435,000,000	2,676,000,000	2,469,000,000	2,431,000,000
Average Securities	260,000,000	313,000,000	251,000,000	362,000,000
Total loans	9,563,000,000	8,790,000,000	9,463,000,000	8,693,000,000
Total deposits	11,165,000,000	10,798,000,000	11,132,000,000	10,546,000,000
Preferred equity	227,000,000	251,000,000	190,000,000	251,000,000
Common equity	1,873,000,000	1,776,000,000	1,861,000,000	1,760,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	2,100,000,000	2,027,000,000	2,051,000,000	2,011,000,000
Number of branches	84		84
NBA [Member]
Segment Reporting Information [Line Items]
Net interest income	40,300,000	41,400,000	80,600,000	81,900,000
Provision for loan losses	(8,000,000)	(4,700,000)	(11,000,000)	(4,700,000)
Net interest income after provision for loan losses	48,300,000	46,100,000	91,600,000	86,600,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	8,300,000	8,800,000	16,600,000	17,000,000
Noninterest expense	38,900,000	35,400,000	76,200,000	69,600,000
Income before income taxes	17,700,000	19,500,000	32,000,000	34,000,000
Income Tax Expense (Benefit)	6,600,000	7,400,000	11,800,000	12,800,000
Net income	11,100,000	12,100,000	20,200,000	21,200,000
Total assets	4,696,000,000	4,620,000,000	4,654,000,000	4,606,000,000
Average cash and due from banks	73,000,000	71,000,000	73,000,000	70,000,000
Average money market investments	413,000,000	433,000,000	351,000,000	456,000,000
Average Securities	371,000,000	300,000,000	368,000,000	287,000,000
Total loans	3,648,000,000	3,612,000,000	3,672,000,000	3,582,000,000
Total deposits	4,014,000,000	3,918,000,000	3,983,000,000	3,906,000,000
Preferred equity	98,000,000	180,000,000	109,000,000	180,000,000
Common equity	454,000,000	407,000,000	438,000,000	404,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	552,000,000	587,000,000	547,000,000	584,000,000
Number of branches	71		71
NSB [Member]
Segment Reporting Information [Line Items]
Net interest income	28,300,000	28,600,000	56,200,000	56,000,000
Provision for loan losses	(5,700,000)	(8,700,000)	(8,300,000)	(8,900,000)
Net interest income after provision for loan losses	34,000,000	37,300,000	64,500,000	64,900,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	8,900,000	9,700,000	13,800,000	18,600,000
Noninterest expense	34,000,000	34,200,000	66,100,000	65,900,000
Income before income taxes	8,900,000	12,800,000	12,200,000	17,600,000
Income Tax Expense (Benefit)	3,000,000	4,400,000	4,000,000	6,000,000
Net income	5,900,000	8,400,000	8,200,000	11,600,000
Total assets	4,073,000,000	4,064,000,000	4,032,000,000	4,058,000,000
Average cash and due from banks	83,000,000	82,000,000	86,000,000	84,000,000
Average money market investments	765,000,000	956,000,000	732,000,000	975,000,000
Average Securities	787,000,000	780,000,000	784,000,000	761,000,000
Total loans	2,318,000,000	2,124,000,000	2,312,000,000	2,111,000,000
Total deposits	3,676,000,000	3,625,000,000	3,637,000,000	3,609,000,000
Preferred equity	50,000,000	113,000,000	50,000,000	126,000,000
Common equity	324,000,000	304,000,000	321,000,000	301,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	374,000,000	417,000,000	371,000,000	427,000,000
Number of branches	48		48
Vectra [Member]
Segment Reporting Information [Line Items]
Net interest income	25,400,000	25,100,000	50,700,000	50,700,000
Provision for loan losses	(4,500,000)	(800,000)	(6,300,000)	(9,400,000)
Net interest income after provision for loan losses	29,900,000	25,900,000	57,000,000	60,100,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	5,900,000	6,100,000	9,700,000	13,100,000
Noninterest expense	23,700,000	25,500,000	49,000,000	50,600,000
Income before income taxes	12,100,000	6,500,000	17,700,000	22,600,000
Income Tax Expense (Benefit)	4,300,000	2,100,000	6,100,000	7,900,000
Net income	7,800,000	4,400,000	11,600,000	14,700,000
Total assets	2,595,000,000	2,529,000,000	2,582,000,000	2,496,000,000
Average cash and due from banks	47,000,000	50,000,000	47,000,000	51,000,000
Average money market investments	18,000,000	78,000,000	16,000,000	62,000,000
Average Securities	158,000,000	184,000,000	161,000,000	184,000,000
Total loans	2,316,000,000	2,138,000,000	2,298,000,000	2,115,000,000
Total deposits	2,184,000,000	2,165,000,000	2,176,000,000	2,136,000,000
Preferred equity	42,000,000	70,000,000	56,000,000	70,000,000
Common equity	283,000,000	237,000,000	265,000,000	232,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	325,000,000	307,000,000	321,000,000	302,000,000
TCBW [Member]
Segment Reporting Information [Line Items]
Net interest income	7,300,000	6,800,000	14,300,000	13,300,000
Provision for loan losses	(400,000)	100,000	300,000	(800,000)
Net interest income after provision for loan losses	7,700,000	6,700,000	14,000,000	14,100,000
Net impairment losses on investment securities	0	0	0	0
Other noninterest income	1,000,000	1,000,000	0	2,000,000
Noninterest expense	5,000,000	3,900,000	9,500,000	8,800,000
Income before income taxes	3,700,000	3,800,000	4,500,000	7,300,000
Income Tax Expense (Benefit)	1,300,000	1,300,000	1,600,000	2,500,000
Net income	2,400,000	2,500,000	2,900,000	4,800,000
Total assets	869,000,000	836,000,000	871,000,000	858,000,000
Average cash and due from banks	21,000,000	19,000,000	21,000,000	19,000,000
Average money market investments	94,000,000	103,000,000	106,000,000	142,000,000
Average Securities	74,000,000	107,000,000	82,000,000	104,000,000
Total loans	665,000,000	595,000,000	648,000,000	580,000,000
Total deposits	734,000,000	703,000,000	738,000,000	719,000,000
Preferred equity	3,000,000	3,000,000	3,000,000	3,000,000
Common equity	92,000,000	84,000,000	90,000,000	83,000,000
Noncontrolling interests	0	0	0	0
Total shareholders' equity	95,000,000	87,000,000	93,000,000	86,000,000
Number of branches	1		1
Other Banks [Member]
Segment Reporting Information [Line Items]
Net interest income	(29,700,000)	(38,600,000)	(60,100,000)	(82,000,000)
Provision for loan losses	0	100,000	0	(400,000)
Net interest income after provision for loan losses	(29,700,000)	(38,700,000)	(60,100,000)	(81,600,000)
Net impairment losses on investment securities	0	(4,200,000)	0	(14,300,000)
Other noninterest income	500,000	(5,700,000)	41,000,000	(9,800,000)
Noninterest expense	8,400,000	38,300,000	13,500,000	50,200,000
Income before income taxes	(37,600,000)	(86,900,000)	(32,600,000)	(155,900,000)
Income Tax Expense (Benefit)	(13,300,000)	(34,700,000)	(11,700,000)	(61,200,000)
Net income	(24,300,000)	(52,200,000)	(20,900,000)	(94,700,000)
Total assets	548,000,000	1,055,000,000	653,000,000	1,130,000,000
Average cash and due from banks	(7,000,000)	(12,000,000)	(12,000,000)	(10,000,000)
Average money market investments	(154,000,000)	220,000,000	(157,000,000)	307,000,000
Average Securities	389,000,000	539,000,000	470,000,000	530,000,000
Total loans	62,000,000	62,000,000	64,000,000	64,000,000
Total deposits	(1,030,000,000)	(689,000,000)	(1,031,000,000)	(477,000,000)
Preferred equity	142,000,000	460,000,000	154,000,000	303,000,000
Common equity	(201,000,000)	(558,000,000)	(209,000,000)	(578,000,000)
Noncontrolling interests	0	(3,000,000)	0	(3,000,000)
Total shareholders' equity	(59,000,000)	(101,000,000)	(55,000,000)	(278,000,000)
Consolidated Company [Member]
Segment Reporting Information [Line Items]
Net interest income	416,300,000	430,700,000	832,800,000	848,800,000
Provision for loan losses	(54,400,000)	(22,000,000)	(55,000,000)	(51,000,000)
Net interest income after provision for loan losses	470,700,000	452,700,000	887,800,000	899,800,000
Net impairment losses on investment securities	0	(4,200,000)	0	(14,300,000)
Other noninterest income	124,900,000	129,300,000	263,200,000	260,600,000
Noninterest expense	406,000,000	451,700,000	804,100,000	849,000,000
Income before income taxes	189,600,000	126,100,000	346,900,000	297,100,000
Income Tax Expense (Benefit)	70,000,000	43,100,000	126,100,000	103,700,000
Net income	119,600,000	83,000,000	220,800,000	193,400,000
Total assets	55,036,000,000	54,664,000,000	55,234,000,000	54,264,000,000
Average cash and due from banks	922,000,000	1,000,000,000	981,000,000	1,032,000,000
Average money market investments	7,501,000,000	8,652,000,000	7,817,000,000	8,384,000,000
Average Securities	4,023,000,000	3,868,000,000	4,070,000,000	3,842,000,000
Total loans	39,544,000,000	37,971,000,000	39,336,000,000	37,786,000,000
Total deposits	45,458,000,000	44,985,000,000	45,617,000,000	44,699,000,000
Preferred equity	1,004,000,000	1,519,000,000	1,004,000,000	1,375,000,000
Common equity	5,745,000,000	5,102,000,000	5,670,000,000	5,046,000,000
Noncontrolling interests	0	(3,000,000)	0	(3,000,000)
Total shareholders' equity	$ 6,749,000,000	$ 6,618,000,000	$ 6,674,000,000	$ 6,418,000,000
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	98		98
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	36		36
New Mexico [Member] | Vectra [Member]
Segment Reporting Information [Line Items]
Number of branches	1		1