Fair Value Measurements - Narrative (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	$ 29,806,144	$ 27,500,136
Amortized cost of fixed maturities	28,418,355	27,111,874
Other investments - structured transactions	276,200	294,000
Spread on U.S. treasury for discounting deposit liabilities	0.465%	0.567%
Corporate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value		11,125,830
Amortized cost of fixed maturities		10,802,332
Medium term notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	152,400	154,600
Amortized cost of fixed maturities	$ 141,100	$ 147,700