Summary of Significant Accounting Policy (Detail) - Jefferson National Financial Corp [Member] $ in Millions	Mar. 01, 2017 USD ($)
Total assets acquired	$ 5,522
Total liabilities assumed	(5,321)
Total consideration	$ 201

Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant