Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions | Common Stock | Additional Paid In Capital | Accumulated Other Comprehensive Income (Loss) | Retained EarningsCumulative Effect, Period of Adoption, AdjustmentSSAT | Retained EarningsCumulative Effect, Period of Adoption, Adjustment | Retained Earnings | Cumulative Effect, Period of Adoption, AdjustmentSSAT | Cumulative Effect, Period of Adoption, Adjustment | Total |
Balance at the beginning of the period at Dec. 31, 2018 | $ 32 | $ 297.8 | $ (34.5) | | | $ 460 | | | $ 755.3 |
Balance (in shares) at Dec. 31, 2018 | 42.7 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | 12.5 | | | 12.5 |
Other comprehensive income (loss), net of tax | | | (0.2) | | | | | | (0.2) |
Share-based compensation | | 3.2 | | | | | | | 3.2 |
Shares issued, net of shares withheld for employee taxes | $ 0.1 | (3.2) | | | | | | | (3.1) |
Shares issued, net of shares withheld for employee taxes (in shares) | 0.1 | | | | | | | | |
Dividends | | | | | | (9.1) | | | (9.1) |
Balance at the end of the period at Mar. 31, 2019 | $ 32.1 | 297.8 | (34.7) | | $ 4.4 | 467.8 | | $ 4.4 | 763 |
Balance (in shares) at Mar. 31, 2019 | 42.8 | | | | | | | | |
Balance at the beginning of the period at Dec. 31, 2018 | $ 32 | 297.8 | (34.5) | | | 460 | | | 755.3 |
Balance (in shares) at Dec. 31, 2018 | 42.7 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | | | | 67.1 |
Other comprehensive income (loss), net of tax | | | | | | | | | (1.2) |
Balance at the end of the period at Sep. 30, 2019 | $ 32.2 | 303.2 | (35.7) | $ (5.6) | | 498 | $ (5.6) | | 797.7 |
Balance (in shares) at Sep. 30, 2019 | 42.9 | | | | | | | | |
Balance at the beginning of the period at Mar. 31, 2019 | $ 32.1 | 297.8 | (34.7) | | $ 4.4 | 467.8 | | $ 4.4 | 763 |
Balance (in shares) at Mar. 31, 2019 | 42.8 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | 18.4 | | | 18.4 |
Other comprehensive income (loss), net of tax | | | (0.5) | | | | | | (0.5) |
Share-based compensation | | 3 | | | | | | | 3 |
Shares issued, net of shares withheld for employee taxes | | (0.1) | | | | | | | (0.1) |
Shares issued, net of shares withheld for employee taxes (in shares) | 0.1 | | | | | | | | |
Dividends | | | | | | (18.6) | | | (18.6) |
Balance at the end of the period at Jun. 30, 2019 | $ 32.1 | 300.7 | (35.2) | | | 467.6 | | | 765.2 |
Balance (in shares) at Jun. 30, 2019 | 42.9 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | 36.2 | | | 36.2 |
Other comprehensive income (loss), net of tax | | | (0.5) | | | | | | (0.5) |
Share-based compensation | | 2.5 | | | | | | | 2.5 |
Shares issued, net of shares withheld for employee taxes | $ 0.1 | | | | | | | | 0.1 |
Dividends | | | | | | (0.2) | | | (0.2) |
Balance at the end of the period at Sep. 30, 2019 | $ 32.2 | 303.2 | (35.7) | $ (5.6) | | 498 | $ (5.6) | | 797.7 |
Balance (in shares) at Sep. 30, 2019 | 42.9 | | | | | | | | |
Balance at the beginning of the period at Dec. 31, 2019 | $ 32.2 | 306.2 | (36.9) | | | 504.2 | | | 805.7 |
Balance (in shares) at Dec. 31, 2019 | 42.9 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | 3.8 | | | 3.8 |
Other comprehensive income (loss), net of tax | | | (0.6) | | | | | | (0.6) |
Share-based compensation | | 3.1 | | | | | | | 3.1 |
Shares issued, net of shares withheld for employee taxes | $ 0.1 | (4.6) | | | | | | | (4.5) |
Shares issued, net of shares withheld for employee taxes (in shares) | 0.1 | | | | | | | | |
Equity interest in SSAT | | | | | | 2.2 | | | 2.2 |
Dividends | | | | | | (9.5) | | | (9.5) |
Balance at the end of the period at Mar. 31, 2020 | $ 32.3 | 304.7 | (37.5) | | | 500.7 | | | 800.2 |
Balance (in shares) at Mar. 31, 2020 | 43 | | | | | | | | |
Balance at the beginning of the period at Dec. 31, 2019 | $ 32.2 | 306.2 | (36.9) | | | 504.2 | | | 805.7 |
Balance (in shares) at Dec. 31, 2019 | 42.9 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | | | | 107.5 |
Other comprehensive income (loss), net of tax | | | | | | | | | (1) |
Balance at the end of the period at Sep. 30, 2020 | $ 32.3 | 312.6 | (37.9) | | | 584.8 | | | 891.8 |
Balance (in shares) at Sep. 30, 2020 | 43.1 | | | | | | | | |
Balance at the beginning of the period at Mar. 31, 2020 | $ 32.3 | 304.7 | (37.5) | | | 500.7 | | | 800.2 |
Balance (in shares) at Mar. 31, 2020 | 43 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | 32.8 | | | 32.8 |
Other comprehensive income (loss), net of tax | | | 0.1 | | | | | | 0.1 |
Share-based compensation | | 3 | | | | | | | 3 |
Shares issued, net of shares withheld for employee taxes | | (1) | | | | | | | (1) |
Shares issued, net of shares withheld for employee taxes (in shares) | 0.1 | | | | | | | | |
Dividends | | | | | | (19.6) | | | (19.6) |
Balance at the end of the period at Jun. 30, 2020 | $ 32.3 | 306.7 | (37.4) | | | 513.9 | | | 815.5 |
Balance (in shares) at Jun. 30, 2020 | 43.1 | | | | | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | | | | | |
Net income | | | | | | 70.9 | | | 70.9 |
Other comprehensive income (loss), net of tax | | | (0.5) | | | | | | (0.5) |
Share-based compensation | | 6 | | | | | | | 6 |
Shares issued, net of shares withheld for employee taxes | | (0.1) | | | | | | | (0.1) |
Balance at the end of the period at Sep. 30, 2020 | $ 32.3 | $ 312.6 | $ (37.9) | | | $ 584.8 | | | $ 891.8 |
Balance (in shares) at Sep. 30, 2020 | 43.1 | | | | | | | | |