Merger, Integration and Other Costs (Summary of Changes in Accrued Severance Related to Restructuring) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Charges	$ 80	$ 9,730
Accrued Severance [Member]
Restructuring Cost And Reserve [Line Items]
Charges		8,782
Payments		(8,375)
Accrued severance as of September 30, 2018	$ 407	$ 407

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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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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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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