Loans - Delinquency Categories by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 23,489	$ 34,808	$ 29,892
31-59 Days Past Due	3,412	13,436
60-89 Days Past Due	1,213	583
90 Days Or More Past Due	18,763	25,584
Total Past Due	23,388	39,603
Current	1,607,402	1,430,180
1-4 family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	12,164	8,470
31-59 Days Past Due	1,012	4,506
60-89 Days Past Due	190	91
90 Days Or More Past Due	11,841	8,470
Total Past Due	13,043	13,067
Current	307,598	202,704
Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	1,113	1,212
31-59 Days Past Due	408	3,411
60-89 Days Past Due	540	321
90 Days Or More Past Due	1,113	1,212
Total Past Due	2,061	4,944
Current	110,297	105,059
Overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total
31-59 Days Past Due
60-89 Days Past Due
90 Days Or More Past Due
Total Past Due
Current	902	1,384
Delinquency Categories [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	372,280	237,789
31-59 Days Past Due	1,136	3,441
60-89 Days Past Due	659	413
90 Days Or More Past Due
Total Past Due	1,795	3,854
Current	370,485	233,935
Delinquency Categories [Member] | 1-4 family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	259,201	126,525
31-59 Days Past Due	705
60-89 Days Past Due	115	91
90 Days Or More Past Due
Total Past Due	820	91
Current	258,381	126,434
Delinquency Categories [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	111,212	108,791
31-59 Days Past Due	408	3,411
60-89 Days Past Due	540	321
90 Days Or More Past Due
Total Past Due	948	3,732
Current	110,264	105,059
Delinquency Categories [Member] | Other Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	965	1,089
31-59 Days Past Due	23	30
60-89 Days Past Due	4	1
90 Days Or More Past Due
Total Past Due	27	31
Current	938	1,058
Delinquency Categories [Member] | Overdrafts [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	902	1,384
31-59 Days Past Due
60-89 Days Past Due
90 Days Or More Past Due
Total Past Due
Current	$ 902	$ 1,384