FAIR VALUE ACCOUNTING AND MEASUREMENT (Fair Value By Balance Sheet Location) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets:
Securities—trading, Fair Value	$ 38,074us-gaap_TradingSecurities	$ 40,258us-gaap_TradingSecurities
Securities—available-for-sale	395,607us-gaap_AvailableForSaleSecurities	411,021us-gaap_AvailableForSaleSecurities
Securities—held-to-maturity	140,499	137,608
Liabilities:
FHLB advances at fair value	250	32,250
Carrying Value
Assets:
Cash and due from banks	298,515	126,072
Securities—trading, Fair Value	38,074	40,258
Securities—available-for-sale	395,607	411,021
Securities—held-to-maturity	133,649	131,258
Loans receivable held for sale	9,419	2,786
Loans receivable	4,105,399	3,831,034
FHLB stock	25,544	27,036
Bank-owned life insurance	71,290	63,759
Mortgage servicing rights	11,709	9,030
Liabilities:
Demand, interest checking and money market accounts	2,561,544	2,227,292
Regular savings	979,824	901,142
Certificates of deposit	778,049	770,516
FHLB advances at fair value	250	32,250
Junior subordinated debentures at fair value	84,326	78,001
Other borrowings	97,020	77,185
Estimated Fair Value
Assets:
Cash and due from banks	298,515	126,072
Securities—trading, Fair Value	38,074	40,258
Securities—available-for-sale	395,607	411,021
Securities—held-to-maturity	140,499	137,608
Loans receivable held for sale	9,847	2,807
Loans receivable	4,003,556	3,722,179
FHLB stock	25,544	27,036
Bank-owned life insurance	71,290	63,759
Mortgage servicing rights	15,425	12,987
Liabilities:
Demand, interest checking and money market accounts	2,332,134	1,998,649
Regular savings	863,499	784,006
Certificates of deposit	772,660	764,549
FHLB advances at fair value	250	32,250
Junior subordinated debentures at fair value	84,326	78,001
Other borrowings	97,020	77,185
Interest Rate Lock Commitments [Member] \| Carrying Value
Assets:
Derivatives:		745	317
Interest Rate Lock Commitments [Member] \| Estimated Fair Value
Assets:
Derivatives:		745	317
Interest rate swaps [Member] \| Carrying Value
Assets:
Derivatives:		8,798	6,290
Liabilities:
Derivatives:		8,798	6,290
Interest rate swaps [Member] \| Estimated Fair Value
Assets:
Derivatives:		8,798	6,290
Liabilities:
Derivatives:		8,798	6,290
Interest Rate Forward Sales Commitments [Member] \| Carrying Value
Liabilities:
Derivatives:		354	198
Interest Rate Forward Sales Commitments [Member] \| Estimated Fair Value
Liabilities:
Derivatives:		$ 354	$ 198

Deposits, Certificates of Deposit, Fair Value Disclosure

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Deposits, Demand NOW and Money Market Accounts, Fair Value Disclosure

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

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of the amount that could be realized under a life insurance contract or contracts owned by the entity, commonly known as corporate-owned life insurance (COLI) or bank-owned life insurance (BOLI).

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of subordinated debt obligations including, but not limited to, subordinated loan, subordinated bond, subordinated debenture or junior debt.

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Fair value portion of borrowing from Federal Home Loan Bank (FHLBank).

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-Topic 942

-SubTopic 210

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-Subparagraph (SX 210.9-03.13(3)(a))

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Fair value of investments in debt securities classified as held-to-maturity.

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Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

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Fair value portion of other liabilities.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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-Subparagraph (SX 210.9-03.4)

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