Credit Quality - Schedule of Age Analysis of its Past Due Loans, Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	$ 173,186	$ 109,640
Loans, 90 Days or more Past Due	73,833	90,002
Loans, Total Past Due	247,019	199,642
Loans, Current	6,466,580	6,318,138
Total gross loans	6,713,599	6,517,780
Loans, Recorded Investment >90 Days & Accruing	11,044	18,068
Owner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	14,144	11,122
Loans, 90 Days or more Past Due	4,537	16,691
Loans, Total Past Due	18,681	27,813
Loans, Current	636,282	701,093
Total gross loans	654,963	728,906
Loans, Recorded Investment >90 Days & Accruing	1,383	4,038
Nonowner-Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	30,836	12,793
Loans, 90 Days or more Past Due	11,725	11,643
Loans, Total Past Due	42,561	24,436
Loans, Current	1,875,224	1,715,984
Total gross loans	1,917,785	1,740,420
Loans, Recorded Investment >90 Days & Accruing	186	2,549
Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	54,319	8,379
Loans, 90 Days or more Past Due	11,794	20,808
Loans, Total Past Due	66,113	29,187
Loans, Current	1,272,242	1,347,896
Total gross loans	1,338,355	1,377,083
Loans, Recorded Investment >90 Days & Accruing	896	1,687
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	54,271	54,168
Loans, 90 Days or more Past Due	25,446	22,095
Loans, Total Past Due	79,717	76,263
Loans, Current	1,741,661	1,761,989
Total gross loans	1,821,378	1,838,252
Loans, Recorded Investment >90 Days & Accruing	5,214	7,363
Construction & Land Development [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	9,921	14,046
Loans, 90 Days or more Past Due	18,491	16,918
Loans, Total Past Due	28,412	30,964
Loans, Current	641,952	519,713
Total gross loans	670,364	550,677
Loans, Recorded Investment >90 Days & Accruing	1,611	654
Bankcard [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	229	394
Loans, 90 Days or more Past Due	128	164
Loans, Total Past Due	357	558
Loans, Current	10,666	10,678
Total gross loans	11,023	11,236
Loans, Recorded Investment >90 Days & Accruing	128	164
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans, 30-89 Days Past Due	9,466	8,738
Loans, 90 Days or more Past Due	1,712	1,683
Loans, Total Past Due	11,178	10,421
Loans, Current	288,553	260,785
Total gross loans	299,731	271,206
Loans, Recorded Investment >90 Days & Accruing	$ 1,626	$ 1,613