Regulatory Matters (Summary Of Actual Capital Amounts And Ratios For The Company And Its Three Largest Subsidiary Banks) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Total capital (to risk-weighted assets), Actual Amount	$ 6,621,539	$ 6,616,521
Capital to Risk Weighted Assets	15.00%	15.05%
Total capital (to risk-weighted assets), To be well capitalized, Amount	4,514,553	4,396,983
Total capital (to risk-weighted assets), To be well capitalized, Ratio	10.00%	10.00%
Tier 1 capital (to risk-weighted assets), Actual Amount	5,763,463	5,883,669
Tier 1 capital (to risk-weighted assets), Actual Ratio	1277.00%	1338.00%
Tier 1 capital (to risk-weighted assets), To be well capitalized, Ratio	600.00%	600.00%
Tier 1 capital (to average assets), Actual Ratio	1048.00%	1096.00%
Parent [Member]
Tier 1 capital (to risk-weighted assets), Actual Amount	5,763,463	5,883,669
Tier 1 capital (to risk-weighted assets), To be well capitalized, Amount	2,708,732	2,638,190
Zions First National Bank [Member]
Total capital (to risk-weighted assets), Actual Amount	1,997,525	2,034,662
Capital to Risk Weighted Assets	1452.00%	1417.00%
Total capital (to risk-weighted assets), To be well capitalized, Amount	1,375,347	1,435,690
Total capital (to risk-weighted assets), To be well capitalized, Ratio	1000.00%	1000.00%
Tier 1 capital (to risk-weighted assets), Actual Amount	1,831,720	1,861,218
Tier 1 capital (to risk-weighted assets), Actual Ratio	1332.00%	1296.00%
Tier 1 capital (to risk-weighted assets), To be well capitalized, Amount	825,208	861,414
Tier 1 capital (to risk-weighted assets), To be well capitalized, Ratio	600.00%	600.00%
Tier 1 capital (to average assets), Actual Ratio	1002.00%	1058.00%
Tier One Leverage Capital Required to be Well Capitalized	913,592	879,719
Tier 1 capital (to average assets), To be well capitalized, Ratio	500.00%	500.00%
CB&T [Member]
Total capital (to risk-weighted assets), Actual Amount	1,252,860	1,222,822
Capital to Risk Weighted Assets	1365.00%	1418.00%
Total capital (to risk-weighted assets), To be well capitalized, Amount	917,950	862,218
Total capital (to risk-weighted assets), To be well capitalized, Ratio	1000.00%	1000.00%
Tier 1 capital (to risk-weighted assets), Actual Amount	1,137,848	1,114,315
Tier 1 capital (to risk-weighted assets), Actual Ratio	1240.00%	1292.00%
Tier 1 capital (to risk-weighted assets), To be well capitalized, Amount	550,770	517,331
Tier 1 capital (to risk-weighted assets), To be well capitalized, Ratio	600.00%	600.00%
Tier 1 capital (to average assets), Actual Ratio	1075.00%	1037.00%
Tier One Leverage Capital Required to be Well Capitalized	529,067	537,534
Tier 1 capital (to average assets), To be well capitalized, Ratio	500.00%	500.00%
Amegy Bank N.A. [Member]
Total capital (to risk-weighted assets), Actual Amount	1,714,314	1,598,708
Capital to Risk Weighted Assets	1486.00%	1517.00%
Total capital (to risk-weighted assets), To be well capitalized, Amount	1,153,382	1,054,110
Total capital (to risk-weighted assets), To be well capitalized, Ratio	1000.00%	1000.00%
Tier 1 capital (to risk-weighted assets), Actual Amount	1,569,696	1,466,001
Tier 1 capital (to risk-weighted assets), Actual Ratio	1361.00%	1391.00%
Tier 1 capital (to risk-weighted assets), To be well capitalized, Amount	692,029	632,466
Tier 1 capital (to risk-weighted assets), To be well capitalized, Ratio	600.00%	600.00%
Tier 1 capital (to average assets), Actual Ratio	1209.00%	1203.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 649,387	$ 609,319
Tier 1 capital (to average assets), To be well capitalized, Ratio	500.00%	500.00%