Revenue Recognition - Quantitative Impact on Financial Statements (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 953.4	$ 1,012.8	$ 1,926.2	$ 1,937.6
Cost of revenues	734.0	769.3	1,473.0	1,495.3
Selling, general and administrative expenses	141.2	127.7	274.9	241.2
Operating income	78.2	115.9	178.3	201.1
Earnings before income taxes	64.3	103.5	153.6	177.8
Provision for income taxes	14.4	41.4	27.0	65.8
Net earnings	$ 49.9	$ 62.1	$ 126.6	$ 112.0
Basic earnings per share (in dollars per share)	$ 0.43	$ 0.53	$ 1.09	$ 0.96
Diluted earnings per share (in dollars per share)	$ 0.42	$ 0.52	$ 1.06	$ 0.93
Current assets	$ 966.4		$ 966.4		$ 991.1
Total assets	3,357.6		3,357.6		3,304.7
Current liabilities	597.9		597.9		777.3
Total liabilities	2,234.9		2,234.9		2,210.4
Total stockholders’ equity	1,122.6		1,122.6		$ 1,094.3
Without Effects of ASU No. 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	1,035.6		2,045.1
Cost of revenues	748.1		1,486.3
Selling, general and administrative expenses	141.6		272.3
Operating income	145.9		286.4
Earnings before income taxes	132.0		261.7
Provision for income taxes	31.0		53.5
Net earnings	$ 101.0		$ 208.2
Basic earnings per share (in dollars per share)	$ 0.87		$ 1.79
Diluted earnings per share (in dollars per share)	$ 0.85		$ 1.74
Current assets	$ 964.1		$ 964.1
Total assets	3,230.7		3,230.7
Current liabilities	589.8		589.8
Total liabilities	2,126.7		2,126.7
Total stockholders’ equity	1,104.0		1,104.0
Effects of ASU 2014-09 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	82.2		118.9
Cost of revenues	14.1		13.3
Selling, general and administrative expenses	0.4		(2.5)
Operating income	67.7		108.1
Earnings before income taxes	67.7		108.1
Provision for income taxes	16.6		26.5
Net earnings	$ 51.1		$ 81.6
Basic earnings per share (in dollars per share)	$ 0.44		$ 0.70
Diluted earnings per share (in dollars per share)	$ 0.43		$ 0.68
Current assets	$ (2.3)		$ (2.3)
Total assets	(126.9)		(126.9)
Current liabilities	(8.1)		(8.1)
Total liabilities	(108.2)		(108.2)
Total stockholders’ equity	$ (18.7)		$ (18.7)