Preferred and Common Stockholder's Equity - Schedule of Stock Repurchases (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Stockholders Equity [Line Items]
Shares purchased and retired		1.6	2.9
Common stock and additional paid-in-capital reductions	$ 11.2	$ 14.5	$ 26.0
Charges to retained earnings	$ 33.3	$ 17.1	$ 81.9
Common Stock [Member]
Stockholders Equity [Line Items]
Shares purchased and retired	1.2	1.6	2.9

Number of shares that have been repurchased and retired during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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