Loans - Schedule of Carrying Amount of Loans Acquired under ASC Topic 310-10 (Detail) - ASC Topic 310-30 - Florida Bank Group, Inc., Old Florida Bancshares, Inc., Georgia Commerce Bancshares, Inc. $ in Thousands	Sep. 30, 2015 USD ($)
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period
Contractually required principal and interest at acquisition	$ 2,402,890
Expected losses and foregone interest	(18,979)
Cash flows expected to be collected at acquisition	2,383,911
Fair value of acquired loans at acquisition	$ 2,130,276