Employee Benefit Plans (Fair Value and Allocation Of Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
BancShares Plan
Defined Benefit Plan Disclosure [Line Items]
Plan assets	544,956	524,017	$ 463,005
Actual % of Plan Assets	100.00%	100.00%
BancShares Plan | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	544,956	524,017
BancShares Plan | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	393,578	380,540
BancShares Plan | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	151,378	143,477
BancShares Plan | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Actual % of Plan Assets	1.00%	1.00%
BancShares Plan | Cash and Cash Equivalents | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%	0.00%
BancShares Plan | Cash and Cash Equivalents | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	1.00%	1.00%
BancShares Plan | Cash and Cash Equivalents | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	3,854	2,517
BancShares Plan | Cash and Cash Equivalents | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	3,854	2,517
BancShares Plan | Cash and Cash Equivalents | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Cash and Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Actual % of Plan Assets	62.00%	62.00%
BancShares Plan | Equity Securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	55.00%	55.00%
BancShares Plan | Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	65.00%	65.00%
BancShares Plan | Equity Securities | Large capitalization | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	229,315	218,023
BancShares Plan | Equity Securities | Large capitalization | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	229,315	218,023
BancShares Plan | Equity Securities | Large capitalization | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | Large capitalization | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | Middle capitalization | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	10,796	10,724
BancShares Plan | Equity Securities | Middle capitalization | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	10,796	10,724
BancShares Plan | Equity Securities | Middle capitalization | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | Middle capitalization | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | Small capitalization | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	44,734	43,928
BancShares Plan | Equity Securities | Small capitalization | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	44,734	43,928
BancShares Plan | Equity Securities | Small capitalization | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | Small capitalization | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | International equity (developed) | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	10,706	10,535
BancShares Plan | Equity Securities | International equity (developed) | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	10,706	10,535
BancShares Plan | Equity Securities | International equity (developed) | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | International equity (developed) | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | International equity (emerging) | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	41,484	40,643
BancShares Plan | Equity Securities | International equity (emerging) | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	41,484	40,643
BancShares Plan | Equity Securities | International equity (emerging) | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Equity Securities | International equity (emerging) | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments
Defined Benefit Plan Disclosure [Line Items]
Actual % of Plan Assets	28.00%	28.00%
BancShares Plan | Fixed Income Investments | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	25.00%	25.00%
BancShares Plan | Fixed Income Investments | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	40.00%	40.00%
BancShares Plan | Fixed Income Investments | Investment grade bonds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	81,050	74,501
BancShares Plan | Fixed Income Investments | Investment grade bonds | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | Investment grade bonds | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	81,050	74,501
BancShares Plan | Fixed Income Investments | Investment grade bonds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | Intermediate bonds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	53,806	48,746
BancShares Plan | Fixed Income Investments | Intermediate bonds | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | Intermediate bonds | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	53,806	48,746
BancShares Plan | Fixed Income Investments | Intermediate bonds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | High-yield corporate bonds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6,592	10,111
BancShares Plan | Fixed Income Investments | High-yield corporate bonds | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | High-yield corporate bonds | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	6,592	10,111
BancShares Plan | Fixed Income Investments | High-yield corporate bonds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | U. S. Treasury | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2,550	4,395
BancShares Plan | Fixed Income Investments | U. S. Treasury | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	2,550	4,395
BancShares Plan | Fixed Income Investments | U. S. Treasury | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | U. S. Treasury | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | International emerging bond | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	9,930	10,119
BancShares Plan | Fixed Income Investments | International emerging bond | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Fixed Income Investments | International emerging bond | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	9,930	10,119
BancShares Plan | Fixed Income Investments | International emerging bond | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Actual % of Plan Assets	9.00%	9.00%
BancShares Plan | Alternative investments | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	0.00%	0.00%
BancShares Plan | Alternative investments | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	10.00%	8.00%
BancShares Plan | Alternative investments | Commodities Investment | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	17,671	19,014
BancShares Plan | Alternative investments | Commodities Investment | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	17,671	19,014
BancShares Plan | Alternative investments | Commodities Investment | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Alternative investments | Commodities Investment | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
BancShares Plan | Alternative investments | Hedge Funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	32,468	30,761
BancShares Plan | Alternative investments | Hedge Funds | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	32,468	30,761
BancShares Plan | Alternative investments | Hedge Funds | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets
BancShares Plan | Alternative investments | Hedge Funds | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Bancorporation Plan
Defined Benefit Plan Disclosure [Line Items]
Plan assets	155,618	150,374
Bancorporation Plan | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	155,618
Bancorporation Plan | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	143,938
Bancorporation Plan | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	11,680
Bancorporation Plan | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Bancorporation Plan | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	35.00%
Actual % of Plan Assets	8.40%
Bancorporation Plan | Cash and Cash Equivalents | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	13,077
Bancorporation Plan | Cash and Cash Equivalents | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	13,077
Bancorporation Plan | Cash and Cash Equivalents | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Bancorporation Plan | Cash and Cash Equivalents | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Bancorporation Plan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	60.00%
Actual % of Plan Assets	68.97%
Bancorporation Plan | Equity Securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	70.00%
Bancorporation Plan | Equity Securities | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	107,333
Bancorporation Plan | Equity Securities | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	107,333
Bancorporation Plan | Equity Securities | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Bancorporation Plan | Equity Securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Bancorporation Plan | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Actual % of Plan Assets	22.62%
Bancorporation Plan | Debt Securities | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	35,208
Bancorporation Plan | Debt Securities | Quoted Prices in Active Markets for Identical Assets and Liabilities (Level 1 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	23,528
Bancorporation Plan | Debt Securities | Quoted Prices for Similar Assets and Liabilities (Level 2 Inputs)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	11,680
Bancorporation Plan | Debt Securities | Fair Value, Inputs, Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0