Segment Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 31, 2018
Segment Reporting Information [Abstract]
Net sales	$ 548.9	$ 508.3	$ 1,115.0	$ 1,023.8
Gross profit	$ 87.9	$ 86.1	$ 182.2	$ 174.6
Gross profit (% of sales)	16.00%	17.00%	16.30%	17.10%
Operating income	$ 22.8	$ 23.5	$ 57.6	$ 51.1
Total assets	1,556.1		1,556.1		$ 1,573.4
Vehicular Thermal Solutions [Member]
Segment Reporting Information [Abstract]
Net sales	335.6	310.6	688.4	625.9
Commercial and Industrial Solutions [Member]
Segment Reporting Information [Abstract]
Net sales	178.2	163.8	362.1	335.2
Building HVAC Systems [Member]
Segment Reporting Information [Abstract]
Net sales	50.7	48.8	95.7	91.8
Total Segments [Member]
Segment Reporting Information [Abstract]
Net sales	564.5	523.2	1,146.2	1,052.9
Operating Segments [Member]
Segment Reporting Information [Abstract]
Net sales	548.9	508.3	1,115.0	1,023.8
Gross profit	$ 87.9	$ 86.0	$ 182.1	$ 174.6
Gross profit (% of sales)	15.60%	16.40%	15.90%	16.60%
Operating income	$ 31.8	$ 34.2	$ 73.7	$ 70.9
Operating Segments [Member] | Vehicular Thermal Solutions [Member]
Segment Reporting Information [Abstract]
Net sales	321.5	296.4	659.8	597.8
Gross profit	$ 44.6	$ 47.1	$ 98.6	$ 97.9
Gross profit (% of sales)	13.30%	15.20%	14.30%	15.60%
Operating income	$ 14.1	$ 18.9	$ 39.6	$ 41.1
Total assets	734.5		734.5		754.8
Operating Segments [Member] | Commercial and Industrial Solutions [Member]
Segment Reporting Information [Abstract]
Net sales	177.4	163.6	360.9	334.7
Gross profit	$ 28.3	$ 24.0	$ 56.9	$ 50.7
Gross profit (% of sales)	15.90%	14.70%	15.70%	15.10%
Operating income	$ 12.9	$ 9.0	$ 26.1	$ 20.4
Total assets	635.5		635.5		630.2
Operating Segments [Member] | Building HVAC Systems [Member]
Segment Reporting Information [Abstract]
Net sales	50.0	48.3	94.3	91.3
Gross profit	$ 15.0	$ 14.9	$ 26.6	$ 26.0
Gross profit (% of sales)	29.50%	30.50%	27.80%	28.30%
Operating income	$ 4.8	$ 6.3	$ 8.0	$ 9.4
Total assets	90.2		90.2		88.1
Corporate and Eliminations [Member]
Segment Reporting Information [Abstract]
Net sales	(15.6)	(14.9)	(31.2)	(29.1)
Gross profit	$ 0.0	$ 0.1	$ 0.1	$ 0.0
Gross profit (% of sales)	0.00%	0.00%	0.00%	0.00%
Operating income	$ (9.0)	$ (10.7)	$ (16.1)	$ (19.8)
Total assets	95.9		95.9		$ 100.3
Inter-segment Sales [Member]
Segment Reporting Information [Abstract]
Net sales	15.6	14.9	31.2	29.1
Inter-segment Sales [Member] | Vehicular Thermal Solutions [Member]
Segment Reporting Information [Abstract]
Net sales	14.1	14.2	28.6	28.1
Inter-segment Sales [Member] | Commercial and Industrial Solutions [Member]
Segment Reporting Information [Abstract]
Net sales	0.8	0.2	1.2	0.5
Inter-segment Sales [Member] | Building HVAC Systems [Member]
Segment Reporting Information [Abstract]
Net sales	$ 0.7	$ 0.5	$ 1.4	$ 0.5