FAIR VALUE MEASUREMENTS - Assets and Liabilities on Recurring Basis (Detail) - USD ($) $ in Thousands		Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		$ 2,855,350	$ 2,231,987
Loans held for sale	[1]	72,585	0
Derivative assets		43,477	54,220
Derivative liabilities		25,428	47,267
U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		19,980	29,953
U.S. Government-Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		355,612	365,098
Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		797,330	535,974
Non-Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		1	897
Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		0	1,291
States of the U.S. and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		30,005	35,849
Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		9,706	9,487
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		166	148
Derivative assets		0	0
Derivative liabilities		0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		2,855,184	2,230,453
Derivative assets		38,908	54,220
Derivative liabilities		25,372	47,267
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Securities available for sale		0	1,386
Derivative assets		4,569	0
Derivative liabilities		56	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		2,854,409	2,231,347
Assets Measured at Fair Value, Equity securities available for sale		941	640
Assets Measured at Fair Value, Securities available for sale		2,855,350	2,231,987
Loans held for sale		72,585
Derivative assets		43,477	54,220
Assets measured at fair value on a recurring basis, Total		2,971,412	2,286,207
Derivative liabilities		25,428	47,267
Liabilities measured at fair value on a recurring basis, Total		25,428	47,267
Fair Value, Measurements, Recurring [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		23,772	45,973
Fair Value, Measurements, Recurring [Member] | Not for Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		1,656	1,294
Fair Value, Measurements, Recurring [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		37,354	44,951
Fair Value, Measurements, Recurring [Member] | Not for Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		6,123	9,269
Fair Value, Measurements, Recurring [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		166
Fair Value, Measurements, Recurring [Member] | Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		775	492
Fair Value, Measurements, Recurring [Member] | Insurance Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0	148
Fair Value, Measurements, Recurring [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		19,980	29,953
Fair Value, Measurements, Recurring [Member] | U.S. Government-Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		355,612	365,098
Fair Value, Measurements, Recurring [Member] | Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		1,641,775	1,252,798
Fair Value, Measurements, Recurring [Member] | Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		797,330	535,974
Fair Value, Measurements, Recurring [Member] | Non-Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		1	897
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	1,291
Fair Value, Measurements, Recurring [Member] | States of the U.S. and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		30,005	35,849
Fair Value, Measurements, Recurring [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		9,706	9,487
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Assets Measured at Fair Value, Equity securities available for sale		166	148
Assets Measured at Fair Value, Securities available for sale		166	148
Loans held for sale		0
Derivative assets		0	0
Assets measured at fair value on a recurring basis, Total		166	148
Derivative liabilities		0	0
Liabilities measured at fair value on a recurring basis, Total		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Not for Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Not for Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		166
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Insurance Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0	148
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | U.S. Government-Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Non-Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | States of the U.S. and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		2,854,409	2,230,453
Assets Measured at Fair Value, Equity securities available for sale		775	0
Assets Measured at Fair Value, Securities available for sale		2,855,184	2,230,453
Loans held for sale		72,585
Derivative assets		38,908	54,220
Assets measured at fair value on a recurring basis, Total		2,966,677	2,284,673
Derivative liabilities		25,372	47,267
Liabilities measured at fair value on a recurring basis, Total		25,372	47,267
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		23,772	45,973
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Not for Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		1,600	1,294
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		37,354	44,951
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Not for Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		1,554	9,269
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		775	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Insurance Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		19,980	29,953
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Government-Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		355,612	365,098
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		1,641,775	1,252,798
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		797,330	535,974
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Non-Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		1	3
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	1,291
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | States of the U.S. and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		30,005	35,849
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		9,706	9,487
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	894
Assets Measured at Fair Value, Equity securities available for sale		0	492
Assets Measured at Fair Value, Securities available for sale		0	1,386
Loans held for sale		0
Derivative assets		4,569	0
Assets measured at fair value on a recurring basis, Total		4,569	1,386
Derivative liabilities		56	0
Liabilities measured at fair value on a recurring basis, Total		56	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Not for Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities		56	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Not for Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		4,569	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Fixed Income Mutual Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Financial Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0	492
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Insurance Services Industry [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Equity securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Treasury [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | U.S. Government-Sponsored Entities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Agency Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Non-Agency Collateralized Mortgage Obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	894
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | States of the U.S. and Political Subdivisions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Other Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Measured at Fair Value, Debt securities available for sale		$ 0	$ 0

[1] Amount represents loans for which we have elected the fair value option. See Note 17.