Loans - Age Analysis of Past Due Loans Including Loans Acquired with Deteriorated Credit Quality (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	$ 7,774	$ 2,139
90 Days and Greater Past Due	11,371	9,567
Total Past Due	19,145	11,706
Current Loans	2,338,632	1,910,511
Loans, gross	2,357,777	1,922,217
Total real estate loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	4,210	1,443
90 Days and Greater Past Due	9,883	7,316
Total Past Due	14,093	8,759
Current Loans	1,444,171	1,252,295
Loans, gross	1,458,264	1,261,054
Other Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	3,564	696
90 Days and Greater Past Due	1,488	2,251
Total Past Due	5,052	2,947
Current Loans	894,461	658,216
Loans, gross	899,513	661,163
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	15
90 Days and Greater Past Due	75	751
Total Past Due	90	751
Current Loans	212,340	167,793
Loans, gross	212,430	168,544
Commercial real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	2,935	960
90 Days and Greater Past Due	7,642	5,914
Total Past Due	10,577	6,874
Current Loans	1,117,604	982,120
Loans, gross	1,128,181	988,994
Consumer real estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	1,260	483
90 Days and Greater Past Due	2,166	651
Total Past Due	3,426	1,134
Current Loans	114,227	102,382
Loans, gross	117,653	103,516
Commercial and industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	3,076	671
90 Days and Greater Past Due	1,281	2,197
Total Past Due	4,357	2,868
Current Loans	878,754	644,222
Loans, gross	883,111	647,090
Other consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Greater Than 30 and Fewer Than 90 Days Past Due	488	25
90 Days and Greater Past Due	207	54
Total Past Due	695	79
Current Loans	15,707	13,994
Loans, gross	$ 16,402	$ 14,073