INVESTMENT SECURITIES (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014 Position	Dec. 31, 2013 Position
Available-for-Sale Portfolio [Abstract]
Amortized Cost	$ 2,447,745	$ 2,217,165
Gross Unrealized Gains	57,779	27,104
Gross Unrealized Losses	11,758	58,106
Fair Value	2,493,766	2,186,163
Other Equity Securities [Abstract]
Amortized Cost	40,653	32,562
Fair Value	40,653	32,562
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Available-for-sale securities in unrealized loss positions less than 12 months qualitative disclosure, number of positions	34	390
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions	162	17
Total available-for-sale securities in unrealized loss positions, number of positions	196	407
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, fair value	51,772	1,451,284
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value	432,309	16,397
Available-for-sale securities, unrealized loss position, fair value	484,081	1,467,681
Available-for-Sale Securities, Debt Maturities, Gross Unrealized Losses [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, gross unrealized losses	279	56,464
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses	11,479	1,642
Available-for-sale securities, unrealized loss position, gross unrealized losses	11,758	58,106
Available-for-Sale Securities, Amortized Cost [Abstract]
Available-for-sale securities, amortized cost, due in one year or less	51,055
Available-for-sale securities, amortized cost, due in one to five years	233,311
Available-for-sale securities, amortized cost, due in five through ten years	1,607,975
Available-for-sale securities, amortized cost, due after ten years	293,058
Available-for-sale securities, amortized cost, with a single maturity date, subtotal	2,185,399
Available-for-sale government agency mortgage-backed securities, amortized cost, without a single maturity date	242,443
Available-for-sale government agency collateralized mortgage obligations, amortized cost, without a single maturity date	19,653
Available-for-sale securities, amortized cost	2,447,495
Available-for-Sale Securities, Fair Value [Abstract]
Available-for-sale securities, fair value, due in one year or less	51,919
Available-for-sale securities, fair value, due in one to five years	240,810
Available-for-sale securities, fair value, due in five through ten years	1,626,370
Available-for-sale securities, fair value, due after ten years	302,637
Available-for-sale securities, fair value with a single maturity date, subtotal	2,221,736
Available-for-sale government agency mortgage-backed securities, fair value, without single maturity date	251,140
Available-for-sale government agency collateralized mortgage obligations, fair value, without single maturity date	20,473
Available-for-sale securities, fair value	2,493,349
U.S. Treasury and Agency Obligations [Member]
Available-for-Sale Portfolio [Abstract]
Amortized Cost	1,474,230	1,252,332
Gross Unrealized Gains	20,605	1,119
Gross Unrealized Losses	7,835	41,304
Fair Value	1,487,000	1,212,147
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Available-for-sale securities in unrealized loss positions less than 12 months qualitative disclosure, number of positions	1	43
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions	14	0
Total available-for-sale securities in unrealized loss positions, number of positions	15	43
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, fair value	23,680	1,181,214
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value	314,400	0
Available-for-sale securities, unrealized loss position, fair value	338,080	1,181,214
Available-for-Sale Securities, Debt Maturities, Gross Unrealized Losses [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, gross unrealized losses	20	41,304
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses	7,815	0
Available-for-sale securities, unrealized loss position, gross unrealized losses	7,835	41,304
Obligations of State and Political Subdivisions [Member]
Available-for-Sale Portfolio [Abstract]
Amortized Cost	684,302	665,441
Gross Unrealized Gains	25,012	15,919
Gross Unrealized Losses	2,056	12,378
Fair Value	707,258	668,982
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Available-for-sale securities in unrealized loss positions less than 12 months qualitative disclosure, number of positions	30	302
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions	118	9
Total available-for-sale securities in unrealized loss positions, number of positions	148	311
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, fair value	20,417	195,526
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value	72,814	4,974
Available-for-sale securities, unrealized loss position, fair value	93,231	200,500
Available-for-Sale Securities, Debt Maturities, Gross Unrealized Losses [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, gross unrealized losses	55	11,774
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses	2,001	604
Available-for-sale securities, unrealized loss position, gross unrealized losses	2,056	12,378
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale Portfolio [Abstract]
Amortized Cost	242,443	250,431
Gross Unrealized Gains	10,476	8,660
Gross Unrealized Losses	1,779	4,113
Fair Value	251,140	254,978
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Available-for-sale securities in unrealized loss positions less than 12 months qualitative disclosure, number of positions	3	43
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions	28	6
Total available-for-sale securities in unrealized loss positions, number of positions	31	49
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, fair value	7,675	68,917
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value	42,319	8,713
Available-for-sale securities, unrealized loss position, fair value	49,994	77,630
Available-for-Sale Securities, Debt Maturities, Gross Unrealized Losses [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, gross unrealized losses	204	3,262
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses	1,575	851
Available-for-sale securities, unrealized loss position, gross unrealized losses	1,779	4,113
Corporate Debt Securities [Member]
Available-for-Sale Portfolio [Abstract]
Amortized Cost	26,867	26,932
Gross Unrealized Gains	699	873
Gross Unrealized Losses	88	218
Fair Value	27,478	27,587
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Available-for-sale securities in unrealized loss positions less than 12 months qualitative disclosure, number of positions	0	1
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions	1	1
Total available-for-sale securities in unrealized loss positions, number of positions	1	2
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, fair value	0	3,026
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value	2,770	2,703
Available-for-sale securities, unrealized loss position, fair value	2,770	5,729
Available-for-Sale Securities, Debt Maturities, Gross Unrealized Losses [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, gross unrealized losses	0	31
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses	88	187
Available-for-sale securities, unrealized loss position, gross unrealized losses	88	218
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Portfolio [Abstract]
Amortized Cost	19,653	21,779
Gross Unrealized Gains	820	362
Gross Unrealized Losses	0	93
Fair Value	20,473	22,048
Available-for-Sale Securities in Unrealized Loss Positions, Number of Positions [Abstract]
Available-for-sale securities in unrealized loss positions less than 12 months qualitative disclosure, number of positions	0	1
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions	1	1
Total available-for-sale securities in unrealized loss positions, number of positions	1	2
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, fair value	0	2,601
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value	6	7
Available-for-sale securities, unrealized loss position, fair value	6	2,608
Available-for-Sale Securities, Debt Maturities, Gross Unrealized Losses [Abstract]
Available-for-sale securities, unrealized loss position, less than 12 months, gross unrealized losses	0	93
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses	0	0
Available-for-sale securities, unrealized loss position, gross unrealized losses	0	93
Marketable Equity Security [Member]
Available-for-Sale Portfolio [Abstract]
Amortized Cost	250	250
Gross Unrealized Gains	167	171
Gross Unrealized Losses	0	0
Fair Value	417	421
Federal Home Loan Bank Common Stock [Member]
Other Equity Securities [Abstract]
Amortized Cost	20,157	12,053
Fair Value	20,157	12,053
Federal Reserve Bank Common Stock [Member]
Other Equity Securities [Abstract]
Amortized Cost	16,050	16,050
Fair Value	16,050	16,050
Other Equity Securities [Member]
Other Equity Securities [Abstract]
Amortized Cost	4,446	4,459
Fair Value	$ 4,446	$ 4,459