Business Combinations - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended								12 Months Ended			0 Months Ended
	Jan. 01, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 01, 2014
Business Acquisition [Line Items]
Shares of common stock authorized		332,023,233				199,629,268				332,023,233	199,629,268
Charge within income tax expense		$ 7,827,000	$ 10,654,000	$ 11,751,000	$ 830,000	$ 16,061,000	$ 7,143,000	$ 10,961,000	$ 12,814,000	$ 31,062,000	$ 46,979,000	$ 66,748,000
Assets acquired:
Goodwill		575,892,000				428,234,000				575,892,000	428,234,000	428,234,000
Deposits:
Number of common stock issued upon exercise of warrant	489,000
Exercise price of warrant (in usd per share)	$ 11.30
State Bancorp Capital Trust I [Member] | New York network [Member]
Deposits:
Number of branches in network										43
First United Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Loans													1,200,000,000
Total deposits													1,400,000,000
Business Acquisition, Share Price (in usd per share)													$ 0.89
Total consideration for acquisition													300,000,000
Cash portion of consideration													8,900,000
Shares issued in acquisition													30,700,000
Shares of common stock authorized			100,000,000
Merger expenses										2,600,000
Charge within income tax expense		7,600,000
Assets acquired:
Cash and cash equivalents													102,025,000
Total investment securities													224,004,000
Non-covered loans													970,570,000
Covered loans													190,282,000
Total loans													1,160,852,000
Premises and equipment													11,234,000
Bank owned life insurance													25,224,000
Accrued interest receivable													3,792,000
FDIC loss-share receivable													7,465,000
Goodwill													147,658,000
Other intangible assets													11,500,000
Other assets													42,876,000
Total assets acquired													1,736,630,000
Deposits:
Non-interest bearing													566,545,000
Savings, NOW and money market													591,749,000
Time													256,549,000
Total deposits													1,414,843,000
Short-term borrowings													16,796,000
Accrued expenses and other liabilities													13,768,000
Total liabilities assumed													1,445,407,000
Common stock issued in acquisition													291,223,000
First United Bancorp, Inc. [Member] | Florida [Member]
Business Acquisition [Line Items]
Number of branches acquired													20
State Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Loans	1,100,000,000
Total deposits	1,400,000,000
Number of branches acquired	16
Total consideration for acquisition	208,000,000
Assets acquired:
Total assets acquired	1,700,000,000
Deposits:
Acquisition date	Jan. 01, 2012
Number of years purchase warrant can be used												10 years
Number of common stock issued upon exercise of warrant										489,000
Exercise price of warrant (in usd per share)		$ 11.30								$ 11.30
State Bancorp, Inc. [Member] | New York network [Member]
Business Acquisition [Line Items]
Number of branches acquired										14
Held-to-maturity Securities [Member] | First United Bancorp, Inc. [Member]
Assets acquired:
Marketable securities													7,930,000
Available for sale securities [Member] | First United Bancorp, Inc. [Member]
Assets acquired:
Marketable securities													$ 216,074,000
Core Deposits [Member]
Deposits:
CDI amortization										11 years
Core Deposits [Member] | First United Bancorp, Inc. [Member]
Deposits:
CDI amortization													11 years