Debt And Shareholders' Equity JUNIOR SUBORDINATED NOTES (Details) - USD ($) $ in Thousands		9 Months Ended
	Jun. 30, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Junior Subordinated Notes		$ 36,083		$ 164,950
AMEGY STATUTORY TRUST ONE [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes		$ 0		51,547
Coupon Rate	3mL+2.85%
Debt Instrument, Date of First Required Payment		Sep. 17, 2016
AMEGY STATUTORY TRUSTS 2 [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes			$ 36,000	36,083
Coupon Rate	3mL+1.90%
Debt Instrument, Date of First Required Payment		Oct. 07, 2016
AMEGY STATUTORY TRUSTS 3 [Member] [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes		$ 0		61,856
Coupon Rate	3mL+1.78%
Debt Instrument, Date of First Required Payment		Sep. 15, 2016
STOCKMEN S STATUTORY TRUST 2 [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes		$ 0		7,732
Coupon Rate	3mL+3.15%
Debt Instrument, Date of First Required Payment		Sep. 26, 2016
STOCKMEN S STATUTORY TRUST 3 [Member]
Debt Instrument [Line Items]
Junior Subordinated Notes		$ 0		$ 7,732
Coupon Rate	3mL+2.89%
Debt Instrument, Date of First Required Payment		Sep. 17, 2016