Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Securitizations and Variable Interest Entities - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Feb. 27, 2015
Variable Interest Entity [Line Items]
Long-term debt	$ 5,404.2	$ 5,801.9
Document Period End Date	Mar. 31, 2018
Collateralized Loan Obligations [Member] \| Salus Capital Partners LLC
Variable Interest Entity [Line Items]
Long-term debt			$ 578.5
Unaffiliated long-term debt of consolidated variable-interest entity \| Salus Capital Partners LLC
Variable Interest Entity [Line Items]
Long-term debt	$ 77.0	28.9
FGL [Member] \| Salus Capital Partners LLC
Variable Interest Entity [Line Items]
Long-term debt		$ 48.1