Business Combinations - Summary of Contractually Required Principal and Interest Cash Payment of the Loans as of Acquisition Date for Purchased Credit Impaired Loans (Detail) (Coastal Bankshares, Inc. [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Jun. 30, 2014
Coastal Bankshares, Inc. [Member]
Business Acquisition [Line Items]
Contractually required principal and interest	$ 38,194
Non-accretable difference	(5,632)
Cash flows expected to be collected	32,562
Accretable yield	(3,282)	(29,300)
Total purchased credit-impaired loans acquired	$ 29,280