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Transactions with Related Persons (Details) - $ / shares				12 Months Ended
	Jul. 13, 2017	Sep. 15, 2016	Apr. 19, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Value of each common share repurchased and retired during the period (in dollars per share)				$ 876.69	$ 869	$ 802
Franklin Mutual Advisers
Related Party Transaction [Line Items]
Value of each common share repurchased and retired during the period (in dollars per share)	$ 850.00	$ 820.00	$ 807.00
Common Stock
Related Party Transaction [Line Items]
Common shares repurchased and retired during the period				592,458	832,725	1,106,145
Common Stock | Franklin Mutual Advisers
Related Party Transaction [Line Items]
Common shares repurchased and retired during the period	235,000	305,000	325,000

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Number of shares that have been repurchased and retired during the period.

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-Topic 210
-SubTopic 10
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Total cost of shares repurchased divided by the total number of shares repurchased.

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