Mergers and Acquisitions - Additional Information (Detail) $ / shares in Units, $ in Thousands										12 Months Ended
	Feb. 13, 2016 USD ($) shares	Sep. 18, 2015 USD ($) Branch	Sep. 03, 2015 USD ($) Branch	Jul. 18, 2015 USD ($)	Jun. 22, 2015 USD ($)	Sep. 19, 2014 USD ($) shares	Feb. 15, 2014 USD ($) shares	Oct. 12, 2013 USD ($) shares	Apr. 06, 2013 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Merger expenses incurred on acquisition										$ 3,033	$ 9,611	$ 8,210
Goodwill recorded as a result of merger										$ 833,086	$ 832,213	$ 764,248
Bank of America [Member]
Business Acquisition [Line Items]
Assets acquired as a result of merger		$ 154,619
Loans acquired as a result of merger		842
Deposits acquired as a result of merger		$ 154,619
Number of branch-banking locations acquired | Branch		5
Cash acquired as a result of merger		$ 148,159
Goodwill and intangible assets acquired as a result of merger		4,485
Fixed and other assets acquired as a result of merger		$ 1,975
Percentage of premium on acquired loan		1.94%
Goodwill deductible for tax purposes		$ 1,485
Other assets recorded as a result of merger		$ 1,133
OBA Financial Services, Inc. (OBA) [Member]
Business Acquisition [Line Items]
Assets acquired as a result of merger						$ 390,160
Loans acquired as a result of merger						291,393
Deposits acquired as a result of merger						295,922
Value of acquisition						$ 85,554
Common shares issued | shares						7,170,037
Common shares acquired | shares						4,025,895
Cash acquired as a result of merger						$ 32,913
Goodwill recorded as a result of merger						20,107
Other assets recorded as a result of merger						21,659
Core deposit intangibles recorded as result of the acquisition						$ 4,304
BCSB Bancorp, Inc. (BCSB) [Member]
Business Acquisition [Line Items]
Assets acquired as a result of merger							$ 596,122
Loans acquired as a result of merger							304,932
Deposits acquired as a result of merger							532,197
Value of acquisition							$ 80,547
Common shares issued | shares							6,730,597
Common shares acquired | shares							3,235,961
Cash acquired as a result of merger							$ 26,980
Goodwill recorded as a result of merger							42,452
Other assets recorded as a result of merger							49,081
Core deposit intangibles recorded as result of the acquisition							$ 6,591
PVF Capital Corp. (PVF) [Member]
Business Acquisition [Line Items]
Assets acquired as a result of merger								$ 737,229
Loans acquired as a result of merger								512,795
Deposits acquired as a result of merger								628,019
Value of acquisition								$ 109,856
Common shares issued | shares								8,893,598
Common shares acquired | shares								26,119,398
Cash acquired as a result of merger								$ 99,738
Goodwill recorded as a result of merger								55,727
Other assets recorded as a result of merger								62,150
Core deposit intangibles recorded as result of the acquisition								$ 6,867
Annapolis Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Assets acquired as a result of merger									$ 430,252
Loans acquired as a result of merger									256,212
Deposits acquired as a result of merger									349,370
Value of acquisition									$ 56,300
Common shares issued | shares									4,641,412
Common shares acquired | shares									4,060,802
Cash acquired as a result of merger									$ 41,986
Goodwill recorded as a result of merger									35,854
Other assets recorded as a result of merger									28,970
Core deposit intangibles recorded as result of the acquisition									3,775
Contingent cash payment due to collection of loan									$ 609
Contingent cash payment due to collection of loan, per share | $ / shares									$ 0.15
Warrants converted to purchase common stock | shares									342,564	364,843
Warrant expiration date									Jan. 30, 2019
Warrant exercise price | $ / shares									$ 3.57	$ 3.38
Metro Bancorp Inc [Member]
Business Acquisition [Line Items]
Merger expenses incurred on acquisition										$ 1,260
Metro Bancorp Inc [Member] | Subsequent Event [Member]
Business Acquisition [Line Items]
Assets acquired as a result of merger	$ 2,854,896
Loans acquired as a result of merger	1,980,790
Deposits acquired as a result of merger	2,326,313
Value of acquisition	$ 402,990
Common shares issued | shares	34,041,181
Common shares acquired | shares	14,345,319
Conway E&S,Inc [Member]
Business Acquisition [Line Items]
Payments to acquire businesses, cash paid				$ 464
Goodwill recorded as a result of merger				269
Other intangibles recorded as a result of merger				$ 195
First Niagara Risk Management Inc [Member]
Business Acquisition [Line Items]
Payments to acquire businesses, cash paid					$ 3,066
Goodwill recorded as a result of merger					1,639
Other intangibles recorded as a result of merger					1,186
Other assets recorded as a result of merger					$ 241
Fifth Third Bank [Member]
Business Acquisition [Line Items]
Deposits acquired as a result of merger			$ 383,000
Number of branch-banking locations acquired | Branch			17