Mergers and Acquisitions - Amounts Recorded on Consolidated Balance Sheets in Conjunction with Acquisition (Detail) - USD ($) $ in Thousands		Feb. 13, 2016	Sep. 19, 2014	Feb. 15, 2014	Dec. 31, 2016	Apr. 22, 2016	Dec. 31, 2015	Sep. 18, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill recognized					$ 1,032,129		$ 833,086		$ 832,213
Fifth Third Bank Branches [Member]
Business Acquisition [Line Items]
Cash and cash equivalents						$ 198,872
Loans						95,354
Core deposit intangibles						4,129
Fixed and other assets						14,069
Total identifiable assets acquired						312,424
Deposits						302,529
Other liabilities						24,041
Total liabilities assumed						326,570
Fair value of net identifiable assets acquired						(14,146)
Goodwill recognized	[1]					$ 14,146
Metro Bancorp Inc [Member]
Business Acquisition [Line Items]
Fair value of consideration paid		$ 404,207
Cash and cash equivalents		46,890
Securities		722,980
Loans		1,862,447
Core deposit intangibles		24,163
Fixed and other assets		127,185
Total identifiable assets acquired		2,783,665
Deposits		2,328,238
Borrowings		227,539
Other liabilities		8,735
Total liabilities assumed		2,564,512
Fair value of net identifiable assets acquired		219,153
Goodwill recognized	[1]	$ 185,054
Bank of America Branches [Member]
Business Acquisition [Line Items]
Cash and cash equivalents								$ 148,159
Loans								842
Core deposit intangibles								3,000
Fixed and other assets								1,133
Total identifiable assets acquired								153,134
Deposits								154,619
Total liabilities assumed								154,619
Fair value of net identifiable assets acquired								(1,485)
Goodwill recognized	[1]							$ 1,485
OBA Financial Services, Inc. (OBA) [Member]
Business Acquisition [Line Items]
Fair value of consideration paid			$ 85,554
Cash and cash equivalents			32,913
Securities			39,891
Loans			291,393
Core deposit intangibles			4,304
Fixed and 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	[1]		$ 20,107
BCSB Bancorp, Inc. (BCSB) [Member]
Business Acquisition [Line Items]
Fair value of consideration paid				$ 80,547
Cash and cash equivalents				26,980
Securities				208,538
Loans				304,932
Core deposit intangibles				6,591
Fixed and other assets				49,081
Total identifiable assets acquired				596,122
Deposits				532,197
Borrowings				17,011
Other liabilities				8,819
Total liabilities assumed				558,027
Fair value of net identifiable assets acquired				38,095
Goodwill recognized	[1]			$ 42,452

[1] All of the goodwill for these transactions has been recorded in the Community Banking segment.