Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Nov. 30, 2018
Organization Consolidation And Presentation [Line Items]
Cash equivalents	$ 136,000		$ 146,100
Weighted average cost of repurchased shares	$ 17.07
Repurchases of common stock under share repurchase program	$ 15,709
Share repurchase program authorized				$ 75,000
Remaining under current repurchase authorization	56,400
Operating lease right-of-use assets	109,448	$ 110,000	$ 0
Operating lease liability	$ 115,200	$ 115,000

[Line Items] for Disclosures of organization, consolidation and basis of presentation of financial statements.

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Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Present value of lessee's discounted obligation for lease payments from operating lease.

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Amount of lessee's right to use underlying asset under operating lease.

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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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