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Amount of stock repurchase plan authorized.

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Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions						12 Months Ended
	Feb. 24, 2020	Nov. 06, 2019	Aug. 06, 2018	May 07, 2018	Feb. 28, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 29, 2020	May 22, 2018
Subsequent Event [Line Items]
Common stock, shares authorized (in shares)						150,000,000	150,000,000			100,000,000
Dividends paid						$ 20.8	$ 18.9	$ 17.2
Dividends paid (in dollars per share)						$ 0.45	$ 0.41	$ 0.37
Dividends declared per share (in dollars per share)		$ 0.12	$ 0.11	$ 0.11	$ 0.11	$ 0.45	$ 0.41	$ 0.37
Number of shares repurchased (in shares)						767,681	588,489	158,106
Average price per share (in dollars per share)						$ 28.66	$ 26.20	$ 28.11
Total repurchase costs						$ 22.0	$ 15.5	$ 4.4
Subsequent Event
Subsequent Event [Line Items]
Dividends declared per share (in dollars per share)	$ 0.12
2020 Program \| Subsequent Event
Subsequent Event [Line Items]
Authorized increase to stock repurchase plan									$ 60.0
2017 Program \| Subsequent Event
Subsequent Event [Line Items]
Common stock available for future share repurchases, amount									$ 0.4