Stock-based Compensation Plans (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	May 21, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			4,236,959
Shares available for issuance (in shares)	3,159,237
Stock-based compensation cost	$ 2.0	$ 1.9
Total unrecognized compensation cost related to non-vested share-based compensation arrangements	$ 14.7
Compensation cost not yet recognized, period for recognition	2 years
Performance-Based Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, number of shares (in shares)	140,536	143,089
Grants in period, weighted average grant date fair value (in dollars per share)	$ 25.32	$ 29.18
2010 LTIP \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, number of shares (in shares)	271,107	218,097
Grants in period, weighted average grant date fair value (in dollars per share)	$ 25.32	$ 29.18

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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