Quarterly Financial Data (Unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2012
Quarterly Financial Data (Unaudited)
Net sales	$ 604.6	$ 566.3	$ 503.5	$ 498.6	$ 611.8	$ 581.4	$ 533.5	$ 544.9	$ 2,173.0	$ 2,271.7	$ 2,028.7
Gross profit	105.6	94.5	95.4	103.3	120.5	101.0	102.6	109.3	398.9	433.5	391.0
Operating income	59.2	49.5	47.5	55.8	65.4	53.0	52.7	61.6	212.0	232.7	210.1
Net income	38.1	30.6	29.5	34.6	40.9	32.9	33.2	39.5	132.8	146.5	121.6
Net income attributable to Carpenter	$ 38.1	$ 30.6	$ 29.5	$ 34.6	$ 40.9	$ 32.9	$ 33.0	$ 39.2	$ 132.8	$ 146.1	$ 121.2
Basic (in dollars per share)	$ 0.71	$ 0.57	$ 0.55	$ 0.65	$ 0.77	$ 0.62	$ 0.62	$ 0.74	$ 2.48	$ 2.75	$ 2.55
Diluted (in dollars per share)	$ 0.71	$ 0.57	$ 0.55	$ 0.65	$ 0.77	$ 0.62	$ 0.62	$ 0.74	$ 2.47	$ 2.73	$ 2.53
Weighted average common shares outstanding, basic	53.4	53.3	53.2	53.1	52.9	52.9	52.9	52.8	53.3	52.9	47.1
Weighted average common shares outstanding, diluted	53.8	53.7	53.6	53.4	53.3	53.2	53.3	53.2	53.6	53.2	47.5