Fair Value Measurements - Narrative (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	$ 29,110,400,000	$ 29,359,034,000
Amortized cost of fixed maturities	27,370,101,000	27,728,771,000
Other investments - structured transactions	354,400,000	354,400,000
Spread on U.S. treasury for discounting deposit liabilities	0.334%	0.295%
Medium term notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	74,800,000	79,900,000
Amortized cost of fixed maturities	$ 63,800,000	$ 68,400,000