Derivative Instruments (Fair Value of Derivative Instruments as Presented in the Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Derivative assets	$ 706,007	$ 337,256
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	706,314	338,666
Derivative liabilities	6,683,046	5,986,761
Call Options [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	706,007	337,256
Interest Rate Caps [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	307	1,410
Fixed Index Annuities - Embedded Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	6,678,102	5,983,622
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 4,944	$ 3,139