INVESTMENT SECURITIES (Details) (USD $) | 3 Months Ended | 12 Months Ended |
In Thousands, unless otherwise specified | Mar. 31, 2014 | Dec. 31, 2013 |
| Position | Position |
Available-for-Sale Portfolio [Abstract] | ' | ' |
Amortized cost | $2,460,730 | $2,217,165 |
Gross unrealized gains | 38,441 | 27,104 |
Gross unrealized losses | 28,885 | 58,106 |
Total available-for-sale investment securities | 2,470,286 | 2,186,163 |
Other Equity Securities [Abstract] | ' | ' |
Amortized cost | 35,935 | 32,562 |
Fair value | 35,935 | 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 | 283 | 390 |
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions | 41 | 17 |
Total available-for-sale securities in unrealized loss positions, number of positions | 324 | 407 |
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract] | ' | ' |
Available-for-sale securities, unrealized loss position, less than 12 months, fair value | 1,044,846 | 1,451,284 |
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value | 28,647 | 16,397 |
Available-for-sale securities, unrealized loss position, fair value | 1,073,493 | 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 | 26,762 | 56,464 |
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses | 2,123 | 1,642 |
Available-for-sale securities, unrealized loss position, gross unrealized losses | 28,885 | 58,106 |
Available-for-Sale Securities, Amortized Cost [Abstract] | ' | ' |
Available-for-sale securities, amortized cost, due in one year or less | 61,273 | ' |
Available-for-sale securities, amortized cost, due in one to five years | 164,805 | ' |
Available-for-sale securities, amortized cost, due in five through ten years | 1,677,793 | ' |
Available-for-sale securities, amortized cost, due after ten years | 287,047 | ' |
Available-for-sale securities, amortized cost, with a single maturity date, subtotal | 2,190,918 | ' |
Available-for-sale government agency mortgage-backed securities, amortized cost, without a single maturity date | 248,785 | ' |
Available-for-sale government agency collateralized mortgage obligations, amortized cost, without a single maturity date | 20,777 | ' |
Available-for-sale securities, amortized cost | 2,460,480 | ' |
Available-for-Sale Securities, Fair Value [Abstract] | ' | ' |
Available-for-sale securities, fair value, due in one year or less | 62,343 | ' |
Available-for-sale securities, fair value, due in one to five years | 169,923 | ' |
Available-for-sale securities, fair value, due in five through ten years | 1,670,155 | ' |
Available-for-sale securities, fair value, due after ten years | 290,993 | ' |
Available-for-sale securities, fair value, subtotal | 2,193,414 | ' |
Available-for-sale government agency mortgage-backed securities, fair value, without single maturity date | 254,850 | ' |
Available-for-sale government agency collateralized mortgage obligations, fair value, without single maturity date | 21,589 | ' |
Available-for-sale securities, fair value | 2,469,853 | ' |
U.S. Treasury and Agency Obligations [Member] | ' | ' |
Available-for-Sale Portfolio [Abstract] | ' | ' |
Amortized cost | 1,479,306 | 1,252,332 |
Gross unrealized gains | 7,582 | 1,119 |
Gross unrealized losses | 20,157 | 41,304 |
Total available-for-sale investment securities | 1,466,731 | 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 | 34 | 43 |
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions | 0 | 0 |
Total available-for-sale securities in unrealized loss positions, number of positions | 34 | 43 |
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract] | ' | ' |
Available-for-sale securities, unrealized loss position, less than 12 months, fair value | 840,063 | 1,181,214 |
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value | 0 | 0 |
Available-for-sale securities, unrealized loss position, fair value | 840,063 | 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 | 20,157 | 41,304 |
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 | 20,157 | 41,304 |
Obligations of State and Political Subdivisions [Member] | ' | ' |
Available-for-Sale Portfolio [Abstract] | ' | ' |
Amortized cost | 684,713 | 665,441 |
Gross unrealized gains | 19,984 | 15,919 |
Gross unrealized losses | 5,571 | 12,378 |
Total available-for-sale investment securities | 699,126 | 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 | 211 | 302 |
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions | 31 | 9 |
Total available-for-sale securities in unrealized loss positions, number of positions | 242 | 311 |
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract] | ' | ' |
Available-for-sale securities, unrealized loss position, less than 12 months, fair value | 139,641 | 195,526 |
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value | 15,923 | 4,974 |
Available-for-sale securities, unrealized loss position, fair value | 155,564 | 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 | 4,355 | 11,774 |
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses | 1,216 | 604 |
Available-for-sale securities, unrealized loss position, gross unrealized losses | 5,571 | 12,378 |
Government Agency Mortgage-Backed Securities [Member] | ' | ' |
Available-for-Sale Portfolio [Abstract] | ' | ' |
Amortized cost | 248,785 | 250,431 |
Gross unrealized gains | 9,086 | 8,660 |
Gross unrealized losses | 3,021 | 4,113 |
Total available-for-sale investment securities | 254,850 | 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 | 38 | 43 |
Available-for-sale securities in unrealized loss positions for 12 months or longer, number of positions | 8 | 6 |
Total available-for-sale securities in unrealized loss positions, number of positions | 46 | 49 |
Available-for-Sale Securities, Debt Maturities, Fair Value [Abstract] | ' | ' |
Available-for-sale securities, unrealized loss position, less than 12 months, fair value | 65,142 | 68,917 |
Available-for-sale securities, unrealized loss position, 12 months or longer, fair value | 9,981 | 8,713 |
Available-for-sale securities, unrealized loss position, fair value | 75,123 | 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 | 2,250 | 3,262 |
Available-for-sale securities, unrealized loss position, 12 months or longer, gross unrealized losses | 771 | 851 |
Available-for-sale securities, unrealized loss position, gross unrealized losses | 3,021 | 4,113 |
Corporate Debt Securities [Member] | ' | ' |
Available-for-Sale Portfolio [Abstract] | ' | ' |
Amortized cost | 26,899 | 26,932 |
Gross unrealized gains | 794 | 873 |
Gross unrealized losses | 136 | 218 |
Total available-for-sale investment securities | 27,557 | 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 | 2,737 | 2,703 |
Available-for-sale securities, unrealized loss position, fair value | 2,737 | 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 | 136 | 187 |
Available-for-sale securities, unrealized loss position, gross unrealized losses | 136 | 218 |
Government Agency Collateralized Mortgage Obligations [Member] | ' | ' |
Available-for-Sale Portfolio [Abstract] | ' | ' |
Amortized cost | 20,777 | 21,779 |
Gross unrealized gains | 812 | 362 |
Gross unrealized losses | 0 | 93 |
Total available-for-sale investment securities | 21,589 | 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 | 183 | 171 |
Gross unrealized losses | 0 | 0 |
Total available-for-sale investment securities | 433 | 421 |
Federal Home Loan Bank Common Stock [Member] | ' | ' |
Other Equity Securities [Abstract] | ' | ' |
Amortized cost | 15,436 | 12,053 |
Fair value | 15,436 | 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 | 4,449 | 4,459 |
Fair value | $4,449 | $4,459 |