Stockholders' Equity - Additional Information (Details) - Common Stock - USD ($) shares in Millions	1 Months Ended	9 Months Ended
Mar. 31, 2018	Sep. 30, 2018
Stockholders Equity [Line Items]
Share repurchase program, authorized amount	$ 200,000,000
Share repurchase program, duration	2 years
Share purchased and retired		3.0
Share purchased and retired, amount		$ 77,200,000

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration