Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Millions, $ in Millions | Common Stock | Additional Paid In Capital | Accumulated Other Comprehensive Income (Loss) | Retained Earnings | Total |
Balance at the beginning of the period at Dec. 31, 2017 | $ 31.9 | $ 289.7 | $ (24.9) | $ 380.5 | $ 677.2 |
Balance (in shares) at Dec. 31, 2017 | 42.5 | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | |
Adoption of new lease accounting standard | | | (6) | 6 | |
Net income | | | | 14.2 | 14.2 |
Other comprehensive income (loss), net of tax | | | 0.2 | | 0.2 |
Share-based compensation | | 2.7 | | | 2.7 |
Shares issued, net of shares withheld for employee taxes | $ 0.1 | (4.3) | | | (4.2) |
Shares issued, net of shares withheld for employee taxes (in shares) | 0.2 | | | | |
Dividends | | | | (8.7) | (8.7) |
Balance at the end of the period at Mar. 31, 2018 | $ 32 | 288.1 | (30.7) | 392 | 681.4 |
Balance (in shares) at Mar. 31, 2018 | 42.7 | | | | |
Balance at the beginning of the period at Dec. 31, 2017 | $ 31.9 | 289.7 | (24.9) | 380.5 | 677.2 |
Balance (in shares) at Dec. 31, 2017 | 42.5 | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | |
Net income | | | | | 88.4 |
Other comprehensive income (loss), net of tax | | | | | (0.6) |
Balance at the end of the period at Sep. 30, 2018 | $ 32 | 293.7 | (31.5) | 448.5 | 742.7 |
Balance (in shares) at Sep. 30, 2018 | 42.7 | | | | |
Balance at the beginning of the period at Mar. 31, 2018 | $ 32 | 288.1 | (30.7) | 392 | 681.4 |
Balance (in shares) at Mar. 31, 2018 | 42.7 | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | |
Net income | | | | 32.6 | 32.6 |
Other comprehensive income (loss), net of tax | | | (0.9) | | (0.9) |
Share-based compensation | | 2.8 | | | 2.8 |
Shares issued, net of shares withheld for employee taxes | | 0.3 | | | 0.3 |
Dividends | | | | (17.7) | (17.7) |
Balance at the end of the period at Jun. 30, 2018 | $ 32 | 291.2 | (31.6) | 406.9 | 698.5 |
Balance (in shares) at Jun. 30, 2018 | 42.7 | | | | |
Increase (Decrease) in Stockholders' Equity | | | | | |
Net income | | | | 41.6 | 41.6 |
Other comprehensive income (loss), net of tax | | | 0.1 | | 0.1 |
Share-based compensation | | 2.7 | | | 2.7 |
Shares issued, net of shares withheld for employee taxes | | (0.2) | | | (0.2) |
Balance at the end of the period at Sep. 30, 2018 | $ 32 | 293.7 | (31.5) | 448.5 | 742.7 |
Balance (in shares) at Sep. 30, 2018 | 42.7 | | | | |
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 | | | | | |
Adoption of new lease accounting standard | | | | 4.4 | 4.4 |
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) | 467.8 | 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) | 498 | 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) | 467.8 | 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 | | | | | |
Adoption of new lease accounting standard | | | | (5.6) | (5.6) |
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) | $ 498 | $ 797.7 |
Balance (in shares) at Sep. 30, 2019 | 42.9 | | | | |