Fair Value Measurements - Schedule of Financial Instruments at Carrying and Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Financial assets:
Cash and cash equivalents	$ 132,439	$ 101,224	$ 80,505	$ 103,823
Securities available for sale	1,156,986	1,157,594
Investment securities held to maturity:
Investment securities held to maturity	454,648	357,500
FHLB-NY stock	70,574	58,070
Loans, net of allowance for loan losses	5,846,194	5,130,149
Financial liabilities:
Certificates of deposit	879,406	806,754
Total deposits	5,838,030	5,202,471
Borrowings	1,418,843	1,203,879
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Cash and cash equivalents	131,064	101,224
Securities available for sale	91,724	93,862
Investment securities held to maturity:
Investment securities held to maturity	7,431	7,470
FHLB-NY stock	70,574	58,070
Loans, net of allowance for loan losses	0	0
Financial liabilities:
Deposits other than certificates of deposits	4,958,624	4,395,717
Certificates of deposit	0	0
Total deposits	4,958,624	4,395,717
Borrowings	0	0
Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Cash and cash equivalents	0	0
Securities available for sale	1,065,262	1,063,732
Investment securities held to maturity:
Investment securities held to maturity	455,846	348,443
FHLB-NY stock	0	0
Loans, net of allowance for loan losses	0	0
Financial liabilities:
Deposits other than certificates of deposits	0	0
Certificates of deposit	885,186	813,337
Total deposits	885,186	813,337
Borrowings	1,429,973	1,218,136
Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Cash and cash equivalents	0	0
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
FHLB-NY stock	0	0
Loans, net of allowance for loan losses	5,971,191	5,221,228
Financial liabilities:
Deposits other than certificates of deposits	0	0
Certificates of deposit	0	0
Total deposits	0	0
Borrowings	0	0
Agency Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Securities available for sale	91,208	93,416
Investment securities held to maturity:
Investment securities held to maturity	7,431	7,470
Agency Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
Agency Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
Mortgage-Backed Securities [Member]
Financial assets:
Securities available for sale	1,048,024	1,054,974
Mortgage-Backed Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
Mortgage-Backed Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Securities available for sale	1,048,024	1,054,974
Investment securities held to maturity:
Investment securities held to maturity	3,866	5,520
Mortgage-Backed Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
State and Municipal Obligations [Member]
Financial assets:
Securities available for sale	7,699	8,758
State and Municipal Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
State and Municipal Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Securities available for sale	7,699	8,758
Investment securities held to maturity:
Investment securities held to maturity	441,868	332,987
State and Municipal Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Securities available for sale	0	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
Equity Securities [Member]
Financial assets:
Securities available for sale	516	446
Equity Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Securities available for sale	516	446
Equity Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Securities available for sale	0	0
Equity Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Securities available for sale	0	0
Corporate Obligations [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial assets:
Securities available for sale	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
Corporate Obligations [Member] | Significant Other Observable Inputs (Level 2) [Member]
Financial assets:
Securities available for sale	9,539
Investment securities held to maturity:
Investment securities held to maturity	10,112	9,936
Corporate Obligations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Financial assets:
Securities available for sale	0
Investment securities held to maturity:
Investment securities held to maturity	0	0
Carrying Value [Member]
Financial assets:
Cash and cash equivalents	131,064	101,224
Securities available for sale	1,156,986	1,157,594
Investment securities held to maturity:
Investment securities held to maturity	454,648	357,500
FHLB-NY stock	70,574	58,070
Loans, net of allowance for loan losses	5,846,194	5,130,149
Financial liabilities:
Deposits other than certificates of deposits	4,958,624	4,395,717
Certificates of deposit	879,406	806,754
Total deposits	5,838,030	5,202,471
Borrowings	1,418,843	1,203,879
Carrying Value [Member] | Agency Obligations [Member]
Financial assets:
Securities available for sale	91,208	93,416
Investment securities held to maturity:
Investment securities held to maturity	7,426	7,523
Carrying Value [Member] | Mortgage-Backed Securities [Member]
Financial assets:
Securities available for sale	1,048,024	1,054,974
Investment securities held to maturity:
Investment securities held to maturity	3,693	5,273
Carrying Value [Member] | State and Municipal Obligations [Member]
Financial assets:
Securities available for sale	7,699	8,758
Investment securities held to maturity:
Investment securities held to maturity	433,464	334,750
Carrying Value [Member] | Equity Securities [Member]
Financial assets:
Securities available for sale	516	446
Carrying Value [Member] | Corporate Obligations [Member]
Financial assets:
Securities available for sale	9,539
Investment securities held to maturity:
Investment securities held to maturity	10,065	9,954
Fair Value [Member]
Financial assets:
Cash and cash equivalents	131,064	101,224
Securities available for sale	1,156,986	1,157,594
Investment securities held to maturity:
Investment securities held to maturity	463,277	355,913
FHLB-NY stock	70,574	58,070
Loans, net of allowance for loan losses	5,971,191	5,221,228
Financial liabilities:
Deposits other than certificates of deposits	4,958,624	4,395,717
Certificates of deposit	885,186	813,337
Total deposits	5,843,810	5,209,054
Borrowings	1,429,973	1,218,136
Fair Value [Member] | Agency Obligations [Member]
Financial assets:
Securities available for sale	91,208	93,416
Investment securities held to maturity:
Investment securities held to maturity	7,431	7,470
Fair Value [Member] | Mortgage-Backed Securities [Member]
Financial assets:
Securities available for sale	1,048,024	1,054,974
Investment securities held to maturity:
Investment securities held to maturity	3,866	5,520
Fair Value [Member] | State and Municipal Obligations [Member]
Financial assets:
Securities available for sale	7,699	8,758
Investment securities held to maturity:
Investment securities held to maturity	441,868	332,987
Fair Value [Member] | Equity Securities [Member]
Financial assets:
Securities available for sale	516	446
Fair Value [Member] | Corporate Obligations [Member]
Financial assets:
Securities available for sale	9,539
Investment securities held to maturity:
Investment securities held to maturity	$ 10,112	$ 9,936