Pension Plan and Employee Benefits - Unobservable Input Reconciliation (Details) - PENSION BENEFITS - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of period	$ 391,933	$ 444,089
Fair value of plan assets at end of period	460,097	391,933
Real estate funds
Defined Benefit Plan, Change in Fair Value of Plan Assets, Level 3 Reconciliation[Roll Forward]
Fair value of plan assets at beginning of period	20,298	19,195
Realized gains (losses)	370	29
Unrealized gains	(1,727)	391
Purchases	759	710
Sales	(1,683)	(27)
Fair value of plan assets at end of period	$ 18,017	$ 20,298

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets sold.

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- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

+ References

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount, measured using unobservable input, of decrease in plan asset of defined benefit plan from sale.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount, measured using unobservable input, of increase in plan asset of defined benefit plan from purchase.

+ References

+ Details

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