Amount of the effect of a change in accounting principle on net income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22583-107794

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22499-107794

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22580-107794

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Basis of Presentation - Additional Information (Detail) - USD ($) shares in Millions, $ in Billions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Basis of Presentation [Line Items]
Restricted stock units outstanding to purchase shares included in diluted earnings per common share	5	5
Accounting Standards Update 2016-15
Basis of Presentation [Line Items]
New accounting standard update			$ 1.1
Accounting Standards Update 2014-09
Basis of Presentation [Line Items]
New accounting standard update			4.2
Accounting Standards Update 2017-07
Basis of Presentation [Line Items]
New accounting standard update			$ 2.2