Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2016	Mar. 31, 2016	Apr. 21, 2016
Stockholders Equity Note [Line Items]
Stock Repurchase Remaining Authorized Amount	$ 4,000	$ 4,000
Dividends, Cash	$ 336	$ 676
Subsequent Event \| Class A common stock
Stockholders Equity Note [Line Items]
Dividends Payable, Amount Per Share			$ 0.14

Amount of paid and unpaid cash dividends declared for classes of stock, for example, but not limited to, common and preferred.

Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6957935&loc=d3e64057-112817

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Balance Type:	debit
Period Type:	duration