Mergers and Acquisitions - Amounts Recorded on Consolidated Balance Sheet in Conjunction with Acquisition (Detail) - USD ($) $ in Thousands	Sep. 19, 2014	Feb. 15, 2014	Oct. 12, 2013	Apr. 06, 2013	Sep. 18, 2015	Dec. 31, 2014
Bank of America [Member]
Business Acquisition [Line Items]
Cash and cash equivalents					$ 148,159
Loans					842
Other intangible assets					3,000
Other assets					1,133
Total identifiable assets acquired					154,619
Deposits					154,619
Total liabilities assumed					154,619
Fair value of net identifiable assets acquired					(1,485)
Goodwill recognized					$ 1,485
OBA Financial Services, Inc. (OBA) [Member]
Business Acquisition [Line Items]
Common stock issued, net of offering costs	$ 85,554
Total consideration paid	85,554
Cash and cash equivalents	32,913
Securities	39,891
Loans	291,393
Other intangible assets	4,304
Other assets	21,659
Total identifiable assets acquired	390,160
Deposits	295,922
Borrowings	27,602
Other liabilities	1,189
Total liabilities assumed	324,713
Fair value of net identifiable assets acquired	65,447
Goodwill recognized	$ 20,107
BCSB Bancorp, Inc. (BCSB) [Member]
Business Acquisition [Line Items]
Common stock issued, net of offering costs		$ 80,547
Total consideration paid		80,547
Cash and cash equivalents		26,980
Securities		208,538
Loans		304,932
Other intangible assets		6,591
Other assets		49,081
Total identifiable assets acquired		596,122
Deposits		532,197
Borrowings		17,011				$ 16,500
Other liabilities		8,819
Total liabilities assumed		558,027
Fair value of net identifiable assets acquired		38,095
Goodwill recognized		$ 42,452
PVF Capital Corp. (PVF) [Member]
Business Acquisition [Line Items]
Common stock issued, net of offering costs			$ 109,856
Total consideration paid			109,856
Cash and cash equivalents			99,738
Securities			47,258
Loans			512,795
Other intangible assets			15,288
Other assets			62,150
Total identifiable assets acquired			737,229
Deposits			628,019
Borrowings			37,241
Other liabilities			17,840
Total liabilities assumed			683,100
Fair value of net identifiable assets acquired			54,129
Goodwill recognized			$ 55,727
Annapolis Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Common stock issued, net of offering costs				$ 54,065
Warrant assumed				2,235
Total consideration paid				56,300
Cash and cash equivalents				41,986
Securities				99,309
Loans				256,212
Other intangible assets				3,775
Other assets				28,970
Total identifiable assets acquired				430,252
Deposits				349,370
Borrowings				58,204
Other liabilities				2,232
Total liabilities assumed				409,806
Fair value of net identifiable assets acquired				20,446
Goodwill recognized				$ 35,854