Related Party Transactions Addtional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended					3 Months Ended	12 Months Ended			9 Months Ended			12 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2014 Jefferies Group Inc [Member]	Sep. 30, 2014 Fortress Investment Group [Member]	Dec. 31, 2012 Registration Rights Agreement	Sep. 30, 2014 Registration Rights Agreement	Sep. 30, 2013 HCP Special Situations Fund	Sep. 30, 2014 Leucadia [Member]	Jun. 30, 2014 Leucadia [Member] Maximum	Jun. 30, 2014 Jefferies [Member]	Dec. 13, 2013 FGL	Sep. 30, 2014 HGI	Sep. 30, 2013 HGI	Sep. 30, 2014 Leucadia [Member] Maximum	Jun. 30, 2014 Preferred Stock [Member] HCP Stockholders [Member]	Mar. 18, 2014 Preferred Stock [Member] HCP Stockholders [Member]	Sep. 30, 2014 Fixed Maturities Securities Fortress Investment Group [Member]	Sep. 30, 2014 Fixed Maturities Securities Leucadia [Member]	Sep. 30, 2014 Fixed Maturities Securities Jefferies [Member]
Related Party Transaction [Line Items]
Document Period End Date		Sep. 30, 2014
Net Investment Income																			$ 1.6	$ 1.1	$ 1.2
Available-for-sale Securities, Noncurrent																			194.9
Services Agreement advance written notice period for termination		30 days
Expenses related to Services Agreement		5.7	4.7	2.0
Secondary offering, shares	23,000,000						23,000,000
Offering cost incurred by company								0.4
Stock Repurchased and Retired During Period, Shares		5,197,000							1,700,000
Common stock repurchased		65.6	12.3											65.6	12.3
Common stock, shares, issued		202,295,600		142,381,100
Sale of Stock, Price Per Share													$ 17
Accrued investment income		184.9	161.2			1.9
Related Party Transaction, Due from (to) Related Party, Noncurrent						196.8
Stock Issued During Period, Shares, Acquisitions																	23,000,000
Share Price																		$ 11
Stock Issued During Period, Value, Acquisitions																	253.0
Percentage Of Beneficial Ownership											27.50%
Limitation of Sale to Third Partyholders of Common Stock, Percent																4.90%
Shares Offered To Public In Initial Offering													9,750,000
Shares Offered To Underwriters In Initial Offering													1,463,000
Expense Related to Distribution or Servicing and Underwriting Fees												0
Gain (Loss) on Sale of Investments					$ 5.8					$ 1.6