Loans and Loans Held for Sale - Restructured Loans for Periods Presented (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended					12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014 Accruing TDRs [Member]	Dec. 31, 2013 Accruing TDRs [Member]	Sep. 30, 2014 Accruing TDRs [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Accruing TDRs [Member] Commercial Real Estate [Member]	Sep. 30, 2014 Accruing TDRs [Member] Commercial and Industrial [Member]	Dec. 31, 2013 Accruing TDRs [Member] Commercial and Industrial [Member]	Sep. 30, 2014 Accruing TDRs [Member] Commercial Construction [Member]	Dec. 31, 2013 Accruing TDRs [Member] Commercial Construction [Member]	Sep. 30, 2014 Accruing TDRs [Member] Residential Mortgage [Member]	Dec. 31, 2013 Accruing TDRs [Member] Residential Mortgage [Member]	Sep. 30, 2014 Accruing TDRs [Member] Home Equity [Member]	Dec. 31, 2013 Accruing TDRs [Member] Home Equity [Member]	Sep. 30, 2014 Accruing TDRs [Member] Installment and Other Consumer [Member]	Dec. 31, 2013 Accruing TDRs [Member] Installment and Other Consumer [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member] Commercial Real Estate [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member] Commercial and Industrial [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member] Commercial and Industrial [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member] Commercial Construction [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member] Commercial Construction [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member] Residential Mortgage [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member] Residential Mortgage [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member] Home Equity [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member] Home Equity [Member]	Sep. 30, 2014 Nonaccruing TDRs [Member] Installment and Other Consumer [Member]	Dec. 31, 2013 Nonaccruing TDRs [Member] Installment and Other Consumer [Member]	Sep. 30, 2014 Total TDRs [Member]	Dec. 31, 2013 Total TDRs [Member]	Sep. 30, 2014 Total TDRs [Member] Commercial Real Estate [Member]	Dec. 31, 2013 Total TDRs [Member] Commercial Real Estate [Member]	Sep. 30, 2014 Total TDRs [Member] Commercial and Industrial [Member]	Dec. 31, 2013 Total TDRs [Member] Commercial and Industrial [Member]	Sep. 30, 2014 Total TDRs [Member] Commercial Construction [Member]	Dec. 31, 2013 Total TDRs [Member] Commercial Construction [Member]	Sep. 30, 2014 Total TDRs [Member] Residential Mortgage [Member]	Dec. 31, 2013 Total TDRs [Member] Residential Mortgage [Member]	Sep. 30, 2014 Total TDRs [Member] Home Equity [Member]	Dec. 31, 2013 Total TDRs [Member] Home Equity [Member]	Sep. 30, 2014 Total TDRs [Member] Installment and Other Consumer [Member]	Dec. 31, 2013 Total TDRs [Member] Installment and Other Consumer [Member]
Financing Receivable, Modifications [Line Items]
Restructured loans	$ 1,179	[1]	$ 1,758	[1]	$ 3,198	[1]	$ 10,036	[1]	$ 37,273	$ 39,229	$ 17,140	$ 19,711	$ 7,401	$ 7,521	$ 6,273	$ 5,338	$ 2,743	$ 2,581	$ 3,594	$ 3,924	$ 122	$ 154	$ 4,929	$ 10,067	$ 898	$ 3,898	$ 1,443	$ 1,884	$ 1,869	$ 2,708	$ 486	$ 1,356	$ 223	$ 218	$ 10	$ 3	$ 42,202	$ 49,296	$ 18,038	$ 23,609	$ 8,844	$ 9,405	$ 8,142	$ 8,046	$ 3,229	$ 3,937	$ 3,817	$ 4,142	$ 132	$ 157

[1] Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.