Loans and Allowance for Credit Losses - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	$ 5,583,000	$ 4,670,000	$ 32,195,000	$ 13,411,000
Transfer to Other Real Estate			8,847,000	4,053,000
Loans held for sale	0		0
Total gains or losses included in earnings	242,000	0	625,000	2,409,000
Nonaccrual	59,929,000		59,929,000		94,518,000
Two Commercial Real Estate Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			21,200,000
Western Pennsylvania Non-Profit Healthcare Facility [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			2,800,000
Western Pennsylvania Student Housing Project [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			3,000,000
Loans to individuals [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non Accrual Status Of Loans After Number Of Days Past Due			150 days
Nonaccrual Commercial Loans [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	32,700,000		32,700,000
Western Pennsylvania Real Estate Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			13,100,000
Nonaccrual Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	2,700,000		2,700,000
Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	2,800,000		2,800,000
Accruing Loans [Member] | Hotel Resort Syndication Loan in the State of Washington [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			3,800,000
Accruing Loans [Member] | Western Pennsylvania Excavation Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			2,300,000
Non Accrual Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			39,800,000
Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			(36,300,000)
Decrease in specific allowance for nonperforming loans			9,500,000
Unfunded commitments related to nonperforming loans	500,000		500,000
Troubled debt restructured loans decreased			34,900,000
Commitments related to troubled debt restructured loans increased			1,700,000
Loans with modifications to rate and payment due to reamortization	0	700,000	600,000	801,000
Impaired Loans [Member] | Reserve for off balance sheet activities [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Off balance sheet reserve to nonperforming loans	200,000		200,000
Impaired Loans [Member] | Real Estate Developer In Eastern Pennsylvania [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			(17,200,000)
Impaired Loans [Member] | Commercial Real Estate Loan in Nevada [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			(2,500,000)
Impaired Loans [Member] | Western Pennsylvania Real Estate Developer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable recorded investment nonaccrual status remaining portion	44,100,000		44,100,000
Impaired Loans [Member] | Western Pennsylvania [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs	2,800,000
Nonaccrual	3,400,000		3,400,000
Impaired Loans [Member] | Construction Loan in Florida [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in nonperforming loans			(3,500,000)
Loans Held For Sale [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gains or losses included in earnings	242,000	0	625,000	2,870,000
Local Energy Company [Member] [Member] | Nonaccrual Commercial Loans [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	12,700,000		12,700,000
Nonaccrual	12,700,000		12,700,000
Western Pennsylvania Specialty Metal Processor [Member] | Nonaccrual Commercial Loans [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,600,000		3,600,000
Nonaccrual	3,500,000		3,500,000
Western Pennsylvania Glass Manufacturer [Member] [Member] | Nonaccrual Commercial Loans [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	3,100,000		3,100,000
Western Pennsylvania Reals Estate Manager [Member] | Nonaccrual Commercial Loans [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual	7,600,000		7,600,000
Western Pennsylvania Real Estate Developer [Member] | Nonaccrual Commercial Loans [Member] [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charge-offs			500,000
Transfer to Other Real Estate			4,800,000
Nonaccrual loans	$ 5,700,000		$ 5,700,000