Investments (Analysis of Past Due Commercial Mortgage and Other Loans) (Details) (Commercial Loan on Other [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Commercial Loan on Other [Member]
Total Past Due	$ 0	$ 0

Recorded Investment in financing receivables that are past due at the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524

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