RETIREMENT AND OTHER EMPLOYEE BENEFITS (Details 2) $ / shares in Units, $ in Thousands | 12 Months Ended | | | |
Dec. 31, 2015USD ($)$ / sharesshares | Dec. 31, 2014USD ($)$ / sharesshares | Dec. 31, 2013USD ($)$ / sharesshares | Dec. 31, 2015USD ($)item$ / sharesshares | Dec. 31, 2014USD ($)$ / sharesshares | Dec. 31, 2013USD ($)$ / sharesshares |
Actual return on plan assets: | | | | | | |
Cash-Equivalent Securities with a maturity | 1 year | | | | | |
Employee Stock Purchase Plan | | | | | | |
Actual return on plan assets: | | | | | | |
Common stock purchase price to eligible employees (as a percent) | 90.00% | | | | | |
Percentage of Black-Scholes methodology used as a component to calculate value of lookback feature | 90.00% | | | | | |
Percentage of maximum subscription price used as a component to calculate value of lookback feature | 10.00% | | | | | |
Shares available for issuance | shares | | | | 764,645 | | |
Subscriptions outstanding (in shares) | shares | | | | 58,742 | 57,369 | 60,413 |
Maximum subscription price (in dollars per share) | $ / shares | | | | $ 21.09 | $ 21.43 | $ 19.58 |
Shares of stock issued | shares | 56,193 | 56,942 | 68,099 | | | |
Stock issuance price (in dollars per share) | $ / shares | | | | $ 21.01 | $ 19.58 | $ 17.95 |
Assumptions for valuation of shares | | | | | | |
Fair value of grants (in dollars per share) | $ / shares | $ 3.58 | $ 3.07 | $ 2.78 | | | |
Risk-free interest rate (as a percent) | 0.26% | 0.10% | 0.14% | | | |
Dividend yield (as a percent) | 4.40% | 4.30% | 4.60% | | | |
Expected volatility (as a percent) | 21.00% | 14.00% | 14.00% | | | |
Expected life in months | 12 months | 12 months | 12 months | | | |
Pension Benefits | | | | | | |
Fair value measurements of plan assets | | | | | | |
Period over which the market-related value is determined | 5 years | | | | | |
Number of basic elements on which primary investment goals of the company for pension fund assets are based (in counts) | item | | | | 4 | | |
Target allocations for plan assets | | | | | | |
Cash investment managers generally hold in their portfolios (as a percent) | 10.00% | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | $ 192,674 | $ 186,547 | $ 186,547 | $ 186,845 | $ 192,674 | $ 186,547 |
Percentage of Plan Assets | | | | 100.00% | 100.00% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 192,674 | 186,547 | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | $ 186,845 | 192,674 | 186,547 | | | |
Pension Benefits | Equity securities | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation (as a percent) | 72.00% | | | | | |
Pension Benefits | Equity securities | High end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, maximum (as a percent) | 80.00% | | | | | |
Pension Benefits | Equity securities | Low end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, minimum (as a percent) | 60.00% | | | | | |
Pension Benefits | Common collective trusts - domestic | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | $ 48,760 | 48,760 | | $ 46,182 | $ 48,760 | |
Percentage of Plan Assets | | | | 24.70% | 25.30% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 48,760 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 46,182 | 48,760 | | | | |
Pension Benefits | Common collective trusts - international | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 42,770 | 42,770 | | $ 41,928 | $ 42,770 | |
Percentage of Plan Assets | | | | 22.50% | 22.20% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 42,770 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 41,928 | 42,770 | | | | |
Pension Benefits | Short term investments | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 70 | 70 | | $ 71 | $ 70 | |
Percentage of Plan Assets | | | | 0.00% | 0.00% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 70 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 71 | 70 | | | | |
Pension Benefits | Equity long/short hedge funds | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 38,428 | 38,428 | | $ 37,970 | $ 38,428 | |
Percentage of Plan Assets | | | | 20.30% | 20.00% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 38,428 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | $ 37,970 | 38,428 | | | | |
Pension Benefits | Fixed income | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation (as a percent) | 28.00% | | | | | |
Pension Benefits | Fixed income | High end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, maximum (as a percent) | 40.00% | | | | | |
Pension Benefits | Fixed income | Low end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, minimum (as a percent) | 20.00% | | | | | |
Pension Benefits | Common collective trust fixed income | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | $ 62,646 | 62,646 | | $ 60,694 | $ 62,646 | |
Percentage of Plan Assets | | | | 32.50% | 32.50% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 62,646 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | $ 60,694 | 62,646 | | | | |
Pension Benefits | Comingled bond funds | | | | | | |
Fund assets measured at fair value | | | | | | |
Maximum high yield | 25.00% | | | | | |
Pension Benefits | Significant Other Observable Inputs (Level 2) | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | $ 154,246 | 154,246 | | $ 148,875 | $ 154,246 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 154,246 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 148,875 | 154,246 | | | | |
Pension Benefits | Significant Other Observable Inputs (Level 2) | Common collective trusts - domestic | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 48,760 | 48,760 | | 46,182 | 48,760 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 48,760 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 46,182 | 48,760 | | | | |
Pension Benefits | Significant Other Observable Inputs (Level 2) | Common collective trusts - international | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 42,770 | 42,770 | | 41,928 | 42,770 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 42,770 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 41,928 | 42,770 | | | | |
Pension Benefits | Significant Other Observable Inputs (Level 2) | Short term investments | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 70 | 70 | | 71 | 70 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 70 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 71 | 70 | | | | |
Pension Benefits | Significant Other Observable Inputs (Level 2) | Common collective trust fixed income | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 62,646 | 62,646 | | 60,694 | 62,646 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 62,646 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 60,694 | 62,646 | | | | |
Pension Benefits | Significant Unobservable Inputs (Level 3) | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 38,428 | 38,428 | | 37,970 | 38,428 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 38,428 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 37,970 | 38,428 | | | | |
Pension Benefits | Significant Unobservable Inputs (Level 3) | Equity long/short hedge funds | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 38,428 | 36,729 | 36,729 | 37,970 | 38,428 | 36,729 |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 38,428 | 36,729 | | | | |
Actual return on plan assets: | | | | | | |
Relating to assets still held at the reporting date | (458) | 1,382 | | | | |
Relating to assets sold during the period | | 1,491 | | | | |
Purchases | | 9,700 | | | | |
Sales | | (10,874) | | | | |
Fair value of plan assets at end of year | 37,970 | 38,428 | 36,729 | | | |
OPEB | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 83,776 | 79,098 | 79,098 | $ 85,369 | $ 83,776 | $ 79,098 |
Percentage of Plan Assets | | | | 100.00% | 100.00% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 83,776 | 79,098 | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | $ 85,369 | 83,776 | $ 79,098 | | | |
OPEB | Equity securities | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation (as a percent) | 60.00% | | | | | |
OPEB | Equity securities | High end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, maximum (as a percent) | 76.00% | | | | | |
OPEB | Equity securities | Low end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, minimum (as a percent) | 44.00% | | | | | |
OPEB | Common collective trust equity securities | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | $ 47,690 | 47,690 | | $ 48,553 | $ 47,690 | |
Percentage of Plan Assets | | | | 56.90% | 56.90% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 47,690 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 48,553 | 47,690 | | | | |
OPEB | Fund assets | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 83,851 | 83,851 | | $ 85,504 | $ 83,851 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 83,851 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | $ 85,504 | 83,851 | | | | |
OPEB | Cash and cash equivalents | High end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation (as a percent) | 10.00% | | | | | |
OPEB | Fixed income | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation (as a percent) | 40.00% | | | | | |
OPEB | Fixed income | High end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, maximum (as a percent) | 44.00% | | | | | |
OPEB | Fixed income | Low end of range | | | | | | |
Target allocations for plan assets | | | | | | |
Target allocation, minimum (as a percent) | 36.00% | | | | | |
OPEB | Common collective trust fixed income | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | $ 33,708 | 33,708 | | $ 34,395 | $ 33,708 | |
Percentage of Plan Assets | | | | 40.30% | 40.20% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 33,708 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 34,395 | 33,708 | | | | |
OPEB | Common collective trusts | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 2,453 | 2,453 | | $ 2,556 | $ 2,453 | |
Percentage of Plan Assets | | | | 3.00% | 2.90% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 2,453 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 2,556 | 2,453 | | | | |
OPEB | Payable for securities purchased | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | (75) | (75) | | $ (135) | $ (75) | |
Percentage of Plan Assets | | | | (0.20%) | 0.00% | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | (75) | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | (135) | (75) | | | | |
OPEB | Significant Other Observable Inputs (Level 2) | Common collective trust equity securities | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 47,690 | 47,690 | | $ 48,553 | $ 47,690 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 47,690 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 48,553 | 47,690 | | | | |
OPEB | Significant Other Observable Inputs (Level 2) | Fund assets | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 83,851 | 83,851 | | 85,504 | 83,851 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 83,851 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 85,504 | 83,851 | | | | |
OPEB | Significant Other Observable Inputs (Level 2) | Common collective trust fixed income | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 33,708 | 33,708 | | 34,395 | 33,708 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 33,708 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | 34,395 | 33,708 | | | | |
OPEB | Significant Other Observable Inputs (Level 2) | Common collective trusts | | | | | | |
Fund assets measured at fair value | | | | | | |
Fair value of plan assets | 2,453 | 2,453 | | $ 2,556 | $ 2,453 | |
Fair Value Measurements Using Significant Unobservable Inputs (Level 3) | | | | | | |
Fair value of plan assets at beginning of year | 2,453 | | | | | |
Actual return on plan assets: | | | | | | |
Fair value of plan assets at end of year | $ 2,556 | $ 2,453 | | | | |
401 (k) plan and ESOP | | | | | | |
Employee 401k and Stock Ownership Plan, ESOP Disclosures [Abstract] | | | | | | |
Maximum percentage of annual compensation to be deferred by participating employees | 25.00% | | | | | |
Shares available to be issued | shares | | | | 129,616 | | |
Shares contributed | shares | 66,783 | 60,049 | 64,128 | | | |
Cash balance formula | | | | | | |
Employee 401k and Stock Ownership Plan, ESOP Disclosures [Abstract] | | | | | | |
Percentage of each employee's deferrals to be matched | 100.00% | | | | | |
Maximum matching contribution as a percentage of employee's eligible compensation | 6.00% | | | | | |
Percentage of matching contribution made in shares | 3.00% | | | | | |
Average annual basic earnings formula | | | | | | |
Employee 401k and Stock Ownership Plan, ESOP Disclosures [Abstract] | | | | | | |
Percentage of each employee's deferrals to be matched | 50.00% | | | | | |
Maximum matching contribution as a percentage of employee's eligible compensation | 3.00% | | | | | |