Loans and Leases (Composition of the Loans and Leases Outstanding By Credit Quality Indicator) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	$ 24,916,700,000	$ 22,833,827,000
PCI commercial loans	606,576,000	762,998,000	$ 809,169,000	$ 950,516,000
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	16,137,227,000	14,799,054,000
PCI commercial loans	296,672,000	393,419,000
Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	757,854,000	669,215,000
Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	10,717,234,000	9,729,022,000
Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	426,985,000	473,433,000
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	3,938,730,000	3,625,208,000
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	296,424,000	302,176,000
Commercial | Pass
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	15,757,669,000	14,348,308,000
PCI commercial loans	141,922,000	201,332,000
Commercial | Pass | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	753,985,000	665,197,000
Commercial | Pass | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	10,507,687,000	9,521,019,000
Commercial | Pass | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	422,500,000	468,942,000
Commercial | Pass | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	3,778,797,000	3,395,086,000
Commercial | Pass | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	294,700,000	298,064,000
Commercial | Special Mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	174,700,000	131,983,000
PCI commercial loans	48,475,000	63,257,000
Commercial | Special Mention | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	1,369,000	691,000
Commercial | Special Mention | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	114,219,000	78,643,000
Commercial | Special Mention | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	3,193,000	1,260,000
Commercial | Special Mention | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	54,814,000	48,470,000
Commercial | Special Mention | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	1,105,000	2,919,000
Commercial | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	127,842,000	161,794,000
PCI commercial loans	101,447,000	117,068,000
Commercial | Substandard | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	2,500,000	3,327,000
Commercial | Substandard | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	92,743,000	128,848,000
Commercial | Substandard | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	1,292,000	3,224,000
Commercial | Substandard | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	30,688,000	25,202,000
Commercial | Substandard | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	619,000	1,193,000
Commercial | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	354,000	647,000
PCI commercial loans	4,828,000	11,735,000
Commercial | Doubtful | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	0
Commercial | Doubtful | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	262,000
Commercial | Doubtful | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	0
Commercial | Doubtful | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	354,000	385,000
Commercial | Doubtful | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	0
Commercial | Ungraded
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	76,662,000	156,322,000
PCI commercial loans	0	27,000
Commercial | Ungraded | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	0
Commercial | Ungraded | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	2,585,000	250,000
Commercial | Ungraded | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	7,000
Commercial | Ungraded | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	74,077,000	156,065,000
Commercial | Ungraded | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	0	0
Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	8,779,473,000	8,034,773,000
Noncommercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	257,030,000	248,289,000
Noncommercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	4,265,687,000	3,523,786,000
Noncommercial | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	2,542,975,000	2,701,525,000
Noncommercial | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	1,713,781,000	1,561,173,000
Non-PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	24,916,700,000	22,833,827,000
Current	24,781,818,000	22,688,955,000
Past Due	134,882,000	144,872,000
Nonaccruing	84,546,000	92,534,000
Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	16,137,227,000	14,799,054,000
Current	16,101,608,000	14,762,509,000
Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	757,854,000	669,215,000
Current	756,885,000	667,925,000
Past Due	969,000	1,290,000
Nonaccruing	666,000	1,040,000
Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	10,717,234,000	9,729,022,000
Current	10,697,731,000	9,707,869,000
Past Due	19,503,000	21,153,000
Nonaccruing	12,594,000	22,625,000
Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	426,985,000	473,433,000
Current	426,518,000	473,251,000
Past Due	467,000	182,000
Nonaccruing	366,000	916,000
Non-PCI Loans | Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	3,938,730,000	3,625,208,000
Current	3,924,424,000	3,611,615,000
Past Due	14,306,000	13,593,000
Nonaccruing	4,624,000	4,876,000
Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	296,424,000	302,176,000
Current	296,050,000	301,849,000
Past Due	374,000	327,000
Non-PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	8,779,473,000	8,034,773,000
Current	8,680,210,000	7,926,446,000
Past Due	99,263,000	108,327,000
Non-PCI Loans | Noncommercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	257,030,000	248,289,000
Current	254,837,000	239,648,000
Past Due	2,193,000	8,641,000
Nonaccruing	1,823,000	1,989,000
Non-PCI Loans | Noncommercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	4,265,687,000	3,523,786,000
Current	4,214,783,000	3,465,935,000
Past Due	50,904,000	57,851,000
Nonaccruing	35,662,000	38,942,000
Non-PCI Loans | Noncommercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccruing	279,000	164,000
Non-PCI Loans | Noncommercial | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	2,542,975,000	2,701,525,000
Current	2,514,269,000	2,674,390,000
Past Due	28,706,000	27,135,000
Nonaccruing	25,563,000	19,990,000
Non-PCI Loans | Noncommercial | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	1,713,781,000	1,561,173,000
Current	1,696,321,000	1,546,473,000
Past Due	17,460,000	14,700,000
Nonaccruing	2,969,000	1,992,000
PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccruing	1,300,000	624,000
PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-PCI Loans	309,904,000	369,579,000
Current	268,280,000	318,632,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	76,187,000	80,031,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	24,747,000	22,751,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	516,000	491,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	14,200,000	12,288,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	91,000	107,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	9,655,000	9,677,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	285,000	188,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	51,440,000	57,280,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	581,000	7,154,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	28,239,000	27,886,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	12,585,000	13,428,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	10,035,000	8,812,000
Financing Receivables, 30 to 59 Days Past Due [Member] | PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	11,155,000	13,343,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	19,682,000	19,050,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	3,910,000	4,500,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	9,000	442,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	2,066,000	2,375,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	76,000	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,759,000	1,677,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	6,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	15,772,000	14,550,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	21,000	108,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	7,357,000	8,064,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	4,490,000	3,485,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	3,904,000	2,893,000
Financing Receivables, 60 to 89 Days Past Due [Member] | PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	7,708,000	6,212,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	39,013,000	45,791,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	6,962,000	9,294,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Commercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	444,000	357,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Commercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	3,237,000	6,490,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Commercial | Other commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	300,000	75,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	2,892,000	2,239,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	89,000	133,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	32,051,000	36,497,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Construction and land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,591,000	1,379,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	15,308,000	21,901,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Revolving mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	11,631,000	10,222,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Non-PCI Loans | Noncommercial | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	3,521,000	2,995,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | PCI Loans | Noncommercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 22,761,000	$ 31,392,000