Loans and Allowance for Credit Losses - Schedule of Receivables for Which Contractually Required Payments would not be Collected (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Monroe Bancorp [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments	$ 94,714
Nonaccretable difference	(45,157)
Cash flows expected to be collected at acquisition	49,557
Accretable yield	(6,971)
Fair value of acquired loans at acquisition	42,586
Integra Bank [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments	921,856
Nonaccretable difference	(226,426)
Cash flows expected to be collected at acquisition	695,430
Accretable yield	(98,487)
Fair value of acquired loans at acquisition	596,943
IBT [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments	118,535
Nonaccretable difference	(53,165)
Cash flows expected to be collected at acquisition	65,370
Accretable yield	(11,945)
Fair value of acquired loans at acquisition	53,425
Tower [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Contractually required payments	22,746
Nonaccretable difference	(5,826)
Cash flows expected to be collected at acquisition	16,920
Accretable yield	(4,065)
Fair value of acquired loans at acquisition	$ 12,855