Common Stock - Narrative (Details) - Share repurchase program approved September 2, 2015 - USD ($)	Jul. 31, 2017	Sep. 02, 2015
Equity, Class of Treasury Stock [Line Items]
Share repurchase program authorized amount		$ 200,000,000.0
Remaining authorized repurchase amount	$ 134,100,000

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.

No definition available.

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