Pension and Other Postretirement Benefit Plans (Contributory employee savings plan) (Details) - USD ($)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Plan Disclosure [Line Items]
Matching contribution, contributory employee savings plan, amount	$ 637,000	$ 547,000	$ 506,000
Postretirement Benefit Plan [Member] \| United States [Member]
Defined Contribution Plan Disclosure [Line Items]
Company matching contribution percentage	50.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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