Related Party (Affiliated Asset Transfers) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Mar. 31, 2012
Related Party Transactions [Abstract]
Fixed maturity asset transfer amortized cost	$ 142.5	$ 123.1
Fixed maturity asset transfer fair value	150.9	141.0
Realized gain on fixed maturity asset transfer	8.4
Commercial mortgage loans asset transfer amortized cost	48.9
Commercial mortgage loans asset transfer fair value	54.2
Realized gain on commerical mortgage loan asset transfer	5.3
Asset Transfer APIC Change		$ 10.6