Reclassifications from Accumulated Other Comprehensive Income (AOCI) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Changes in the balance of Accumulated Other Comprehensive Income
Balance at the beginning of the period	$ (282.8)	$ (317.2)	$ (245.2)	$ (335.7)
Other comprehensive income (loss) before reclassifications	(26.8)	16.0	(70.5)	17.7
Amounts reclassified from AOCI	6.7	7.2	12.8	24.0
Other comprehensive (loss) income	(20.1)	23.2	(57.7)	41.7
Balance at the end of the period	(302.9)	(294.0)	(302.9)	(294.0)
Cash flow hedging items
Changes in the balance of Accumulated Other Comprehensive Income
Balance at the beginning of the period	(17.9)	(35.5)	7.6	(41.5)
Other comprehensive income (loss) before reclassifications	(16.9)	17.0	(42.6)	13.7
Amounts reclassified from AOCI	3.7	3.5	3.9	12.8
Other comprehensive (loss) income	(13.2)	20.5	(38.7)	26.5
Balance at the end of the period	(31.1)	(15.0)	(31.1)	(15.0)
Pension and other postretirement benefit plan items
Changes in the balance of Accumulated Other Comprehensive Income
Balance at the beginning of the period	(230.8)	(266.1)	(236.7)	(273.6)
Other comprehensive income (loss) before reclassifications	0	0	0	0
Amounts reclassified from AOCI	3.0	3.7	8.9	11.2
Other comprehensive (loss) income	3.0	3.7	8.9	11.2
Balance at the end of the period	(227.8)	(262.4)	(227.8)	(262.4)
Unrealized losses on available-for-sale securities
Changes in the balance of Accumulated Other Comprehensive Income
Balance at the beginning of the period	(0.4)	(0.3)	(0.4)	(0.4)
Other comprehensive income (loss) before reclassifications	0	0	0	0.1
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive (loss) income	0	0	0	0.1
Balance at the end of the period	(0.4)	(0.3)	(0.4)	(0.3)
Foreign currency items
Changes in the balance of Accumulated Other Comprehensive Income
Balance at the beginning of the period	(33.7)	(15.3)	(15.7)	(20.2)
Other comprehensive income (loss) before reclassifications	(9.9)	(1.0)	(27.9)	3.9
Amounts reclassified from AOCI	0	0	0	0
Other comprehensive (loss) income	(9.9)	(1.0)	(27.9)	3.9
Balance at the end of the period	(43.6)	(16.3)	(43.6)	(16.3)
Foreign currency items | Kalyani Carpenter Special Steels Ltd.
Changes in the balance of Accumulated Other Comprehensive Income
Balance at the beginning of the period					4.9
Balance at the end of the period					$ 4.9