INVESTMENTS IN DEBT AND EQUITY SECURITIES (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	$ 39,151	$ 28,514
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	163,418	169,684
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	180,752	139,283
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	1,151,372	1,096,365
Carrying value: Total Amortized Cost	1,534,693	1,433,846
Available-for-sale Securities, Gross Unrealized Gains	23,866	19,168
Available-for-sale Securities, Gross Unrealized Losses	(4,117)	(7,325)
Available-for-sale Securities, Fair Value	1,554,442us-gaap_AvailableForSaleSecurities	1,445,689us-gaap_AvailableForSaleSecurities
Available-for-sale Securities Weighted Average Yield	2.23%	2.25%
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	39,606	28,901
Available-for-sale Securities, Debt Maturities, Year One Through Five, Fair Value	166,357	172,561
Available-for-sale Securities, Debt Maturities, Year Five Through Ten, Fair Value	184,307	140,717
Available-for-sale Securities, Debt Maturities, After Ten Years, Fair Value	1,164,172	1,103,510
Available-for-sale Securities Weighted Average Yield With In One Year	2.57%	2.64%
Available-for-sale Securities Weighted Average Yield After One Through Five Years	1.96%	1.97%
Available-for-sale Securities Weighted Average Yield After Five Through Ten Years	2.58%	2.58%
Available-for-sale Securities Weighted Average Yield After Ten Years	2.20%	2.23%
U.S. Government sponsored agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	0	0
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	29,904	29,942
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	20,114	20,119
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	201,168	180,098
Carrying value: Total Amortized Cost	251,186	230,159
Available-for-sale Securities, Gross Unrealized Gains	2,093	2,129
Available-for-sale Securities, Gross Unrealized Losses	(727)	(557)
Available-for-sale Securities, Fair Value	252,552	231,731
Available-for-sale Securities Weighted Average Yield	1.45%	1.39%
Residential mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	0	269
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	65,101	65,433
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	79,250	48,174
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	895,399	885,896
Carrying value: Total Amortized Cost	1,039,750	999,772
Available-for-sale Securities, Gross Unrealized Gains	18,814	14,189
Available-for-sale Securities, Gross Unrealized Losses	(2,308)	(6,117)
Available-for-sale Securities, Fair Value	1,056,256	1,007,844
Available-for-sale Securities Weighted Average Yield	2.38%	2.39%
Commercial mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	0	0
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	775	779
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	0	0
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	0	0
Carrying value: Total Amortized Cost	775	779
Available-for-sale Securities, Gross Unrealized Gains	63	58
Available-for-sale Securities, Gross Unrealized Losses	0	0
Available-for-sale Securities, Fair Value	838	837
Available-for-sale Securities Weighted Average Yield	4.95%	4.95%
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	511	863
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	569	571
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	0	0
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	28,356	28,371
Carrying value: Total Amortized Cost	29,436	29,805
Available-for-sale Securities, Gross Unrealized Gains	26	33
Available-for-sale Securities, Gross Unrealized Losses	(268)	(223)
Available-for-sale Securities, Fair Value	29,194	29,615
Available-for-sale Securities Weighted Average Yield	1.04%	1.05%
Corporate notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	38,640	27,382
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	67,069	72,959
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	81,388	70,990
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	24,449	0
Carrying value: Total Amortized Cost	211,546	171,331
Available-for-sale Securities, Gross Unrealized Gains	2,870	2,759
Available-for-sale Securities, Gross Unrealized Losses	(799)	(395)
Available-for-sale Securities, Fair Value	213,617	173,695
Available-for-sale Securities Weighted Average Yield	2.55%	2.75%
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Maturities With In One Year, Amortized Cost	0	0
Available-for-sale Securities, Maturities After One Through Five Years, Amortized Cost	0	0
Available-for-sale Securities, Maturities After Five Through Ten Years, Amortized Cost	0	0
Available-for-sale Securities, Maturities After Ten Years, Amortized Cost	2,000	2,000
Carrying value: Total Amortized Cost	2,000	2,000
Available-for-sale Securities, Gross Unrealized Gains	0	0
Available-for-sale Securities, Gross Unrealized Losses	(15)	(33)
Available-for-sale Securities, Fair Value	1,985	1,967
Available-for-sale Securities Weighted Average Yield	2.14%	2.15%
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year One Through Five, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, Year Five Through Ten, Fair Value	0	0
Available-for-sale Securities, Debt Maturities, After Ten Years, Fair Value	1,985	1,967
Debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	39,606	28,901
Available-for-sale Securities, Debt Maturities, Year One Through Five, Fair Value	166,357	172,561
Available-for-sale Securities, Debt Maturities, Year Five Through Ten, Fair Value	184,307	140,717
Available-for-sale Securities, Debt Maturities, After Ten Years, Fair Value	$ 1,162,187	$ 1,101,543

The percentage of available for sale securities weighted average yield.

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The percentage of available for sale securities weighted average yield, maturing in the fifth through tenth fiscal year following the latest fiscal year.

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The percentage of available for sale securities weighted average yield, maturing in the next fiscal year through the fifth fiscal year following the latest fiscal year.

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The percentage of available for sale securities weighted average yield, maturing after the tenth fiscal year following the latest fiscal year.

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The percentage of available for sale securities weighted average yield, maturing in the next fiscal year following the latest fiscal year.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after adjustments of available-for-sale debt securities at cost, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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