Annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan.

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Defined benefit plan unrecognized service cost amortization period.

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- Definition

Employee Contribution Percentage

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Employees Additional Eligible Automatic Contribution

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Employees age limit to be eligible for participation in defined contribution plan.

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Employees Eligible Automatic Contribution

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- Definition

Increased annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan.

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Number of supplemental non qualified retirement plans.

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Percent of employee contribution matched by corporation

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Post Retirement Benefits, Benefit Calculation, Number Of Consecutive Years

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Post Retirement Benefits, Benefit Calculation, Number Of Years

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- Definition

pre medicare eligible postretirement medical insurance plan employees age limit to be eligible for employer-paid coverage.

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Pre medicare eligible postretirement medical insurance plan maximum age limit.

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Pre Medicare eligible postretirement medical insurance plan minimum age limit.

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Amount related to the pretax cost of benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation, which has not yet been recognized as components of net periodic benefit cost.

+ References

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The amounts in accumulated other comprehensive income related to prior service cost or credit expected to be recognized as components of net periodic benefit cost over the next fiscal year that follows the most recent annual statement of financial position presented.

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The amount of the cost recognized during the period for defined contribution plans.

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Retirement And Other Postretirement Benefit Plans (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2011	Jan. 31, 2008	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2008	Jan. 01, 2007 years
Retirement And Other Postretirement Benefit Plans [Abstract]
Net unrecognized service credit								$ 14,079
Number of years for which net unrecognized service credit is being amortized								13.5
Unrecognized prior service credit included in income						10,543
Number of supplemental non-qualified retirement plans sponsored by the Corporation			2
Number of consecutive calendar years used to calculate BRP benefits							5
Number of years used to calculate BRP benefits							10
Percent of employer match					100.00%	50.00%
Employee contribution percentage					4.00%	6.00%
Annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan			3.00%
Employees' required age to be eligible for participation in defined contribution plan, minimum			21
Increase in annuity equivalent of contribution to defined contribution plan deducted from monthly benefit of basic retirement plan for full-time employees		4.00%
Additional automatic contribution increase, performance goals, percentage							2.00%
Contribution expense of the Corporation			$ 6,222	$ 3,724
Automatic contribution increase available under contribution method each calendar year, percentage	3.00%
Pre-Medicare eligible postretirement medical insurance plan minimum age limit			62
Pre-Medicare eligible postretirement medical insurance plan employees age limit to be eligible for employer-paid coverage								60 or older
Pre-Medicare eligible postretirement medical insurance plan maximum age limit			65