Stock-Based Compensation - Plan Information (Details) - 2012 Plan - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Stock based compensation
Number of awards approved for grant (in shares)	4,000,000		4,000,000
Common stock remaining available for issuance (in shares)	22,785		22,785
Compensation expense	$ 3.3	$ 2.5	$ 7.1	$ 5.0
Board of Directors
Stock based compensation
Common shares granted to members of board of directors as compensation for director services			18,397	14,895

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

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