Consolidated Statements of Equity (Unaudited) - USD ($) $ in Millions	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Balance (in shares) at Dec. 31, 2019	18,336,010
Balance at Dec. 31, 2019	$ 6.9	$ 45.5	$ 346.0	$ (38.5)	$ 359.9	$ 1.4	$ 361.3
Net income (loss)	0.0	0.0	5.2	0.0	5.2	0.0	5.2
Other comprehensive income (loss)	$ 0.0	0.0	0.0	(7.6)	(7.6)	0.0	(7.6)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares (in shares)	98,805
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares	$ 0.0	1.1	0.0	0.0	1.1	0.0	1.1
Share-based compensation	0.0	2.8	0.0	0.0	2.8	0.0	2.8
Dividends paid per common share	0.0	0.0	(4.0)	0.0	(4.0)	0.0	(4.0)
Other	$ 0.0	0.0	(0.1)	0.0	(0.1)	0.0	(0.1)
Balance (in shares) at Mar. 31, 2020	18,434,815
Balance at Mar. 31, 2020	$ 6.9	49.4	347.1	(46.1)	357.3	1.4	358.7
Balance (in shares) at Dec. 31, 2019	18,336,010
Balance at Dec. 31, 2019	$ 6.9	45.5	346.0	(38.5)	359.9	1.4	361.3
Net income (loss)							$ 31.2
Repurchases of common stock (in shares)							0
Balance (in shares) at Sep. 30, 2020	18,473,149
Balance at Sep. 30, 2020	$ 6.9	52.2	365.0	(30.2)	393.9	1.4	$ 395.3
Balance (in shares) at Mar. 31, 2020	18,434,815
Balance at Mar. 31, 2020	$ 6.9	49.4	347.1	(46.1)	357.3	1.4	358.7
Net income (loss)	0.0	0.0	14.3	0.0	14.3	0.0	14.3
Other comprehensive income (loss)	$ 0.0	0.0	0.0	4.1	4.1	0.0	4.1
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares (in shares)	20,647
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares	$ 0.0	0.0	0.0	0.0	0.0	0.0	0.0
Dividends paid per common share	$ 0.0	0.0	(4.0)	0.0	(4.0)	0.0	(4.0)
Balance (in shares) at Jun. 30, 2020	18,455,462
Balance at Jun. 30, 2020	$ 6.9	49.4	357.4	(42.0)	371.7	1.4	373.1
Net income (loss)	0.0	0.0	11.7	0.0	11.7	0.0	11.7
Other comprehensive income (loss)	$ 0.0	0.0	0.0	11.8	11.8	0.0	11.8
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares (in shares)	17,687
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares	$ 0.0	0.9	0.0	0.0	0.9	0.0	0.9
Share-based compensation	0.0	1.9	0.0	0.0	1.9	0.0	1.9
Dividends paid per common share	$ 0.0	0.0	(4.1)	0.0	(4.1)	0.0	(4.1)
Balance (in shares) at Sep. 30, 2020	18,473,149
Balance at Sep. 30, 2020	$ 6.9	52.2	365.0	(30.2)	393.9	1.4	$ 395.3
Balance (in shares) at Dec. 31, 2020	18,503,805						18,503,805
Balance at Dec. 31, 2020	$ 6.9	54.7	363.3	(20.1)	404.8	1.3	$ 406.1
Net income (loss)	0.0	0.0	25.7	0.0	25.7	0.0	25.7
Other comprehensive income (loss)	$ 0.0	0.0	0.0	(10.7)	(10.7)	0.0	(10.7)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares (in shares)	102,681
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares	$ 0.1	1.3	0.0	0.0	1.4	0.0	1.4
Share-based compensation	0.0	3.1	0.0	0.0	3.1	0.0	3.1
Dividends paid per common share	$ 0.0	0.0	(4.2)	0.0	(4.2)	0.0	(4.2)
Balance (in shares) at Mar. 31, 2021	18,606,486
Balance at Mar. 31, 2021	$ 7.0	59.1	384.8	(30.8)	420.1	1.3	$ 421.4
Balance (in shares) at Dec. 31, 2020	18,503,805						18,503,805
Balance at Dec. 31, 2020	$ 6.9	54.7	363.3	(20.1)	404.8	1.3	$ 406.1
Net income (loss)							$ 57.0
Repurchases of common stock (in shares)							(102,229)
Balance (in shares) at Sep. 30, 2021	18,583,237						18,583,237
Balance at Sep. 30, 2021	$ 7.0	60.8	407.4	(33.4)	441.8	1.3	$ 443.1
Balance (in shares) at Mar. 31, 2021	18,606,486
Balance at Mar. 31, 2021	$ 7.0	59.1	384.8	(30.8)	420.1	1.3	421.4
Net income (loss)	0.0	0.0	9.8	0.0	9.8	0.0	9.8
Other comprehensive income (loss)	$ 0.0	0.0	0.0	4.9	4.9	0.0	4.9
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares (in shares)	58,579
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares	$ 0.0	1.9	0.0	0.0	1.9	0.0	1.9
Share-based compensation	0.0	3.9	0.0	0.0	3.9	0.0	3.9
Dividends paid per common share	$ 0.0	0.0	(4.4)	0.0	(4.4)	0.0	(4.4)
Balance (in shares) at Jun. 30, 2021	18,665,065
Balance at Jun. 30, 2021	$ 7.0	64.9	390.2	(25.9)	436.2	1.3	437.5
Net income (loss)	0.0	0.0	21.5	0.0	21.5	0.0	21.5
Other comprehensive income (loss)	$ 0.0	0.0	0.0	(7.5)	(7.5)	0.0	(7.5)
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares (in shares)	20,401
Issue stock for directors, employee benefit and stock plans, net of related tax withholdings of shares	$ 0.0	0.9	0.0	0.0	0.9	0.0	0.9
Share-based compensation	0.0	2.5	0.0	0.0	2.5	0.0	2.5
Dividends paid per common share	$ 0.0	0.0	(4.3)	0.0	(4.3)	0.0	(4.3)
Repurchases of common stock (in shares)	(102,229)
Repurchases of common stock	$ 0.0	(7.5)	0.0	0.0	(7.5)	0.0	$ (7.5)
Balance (in shares) at Sep. 30, 2021	18,583,237						18,583,237
Balance at Sep. 30, 2021	$ 7.0	$ 60.8	$ 407.4	$ (33.4)	$ 441.8	$ 1.3	$ 443.1