Sale of Trust Accounts - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Apr. 30, 2015	Mar. 31, 2015
Discontinued Operations and Disposal Groups [Abstract]
Gain on sale of business net of tax	$ 23
Gain on sale of business before tax	45
Goodwill recorded	$ 11
Revenue on sale of business		$ 9

Amount before tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 45
-Paragraph 3B
-URI http://asc.fasb.org/extlink&oid=51716988&loc=SL51721525-107759

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Amount after tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
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-URI http://asc.fasb.org/extlink&oid=51717284&loc=d3e1361-107760

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Amount classified as goodwill attributable to disposal group held for sale or disposed of.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of revenue attributable to disposal group, including, but not limited to, discontinued operation.

+ References

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