Fair Values of Financial Instruments (Assumptions Used in Estimating Fair Value) (Details) - Fixed Index Annuities [Member]	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Minimum [Member] | Contract Duration (Years), Group 1 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	1 year	1 year
Minimum [Member] | Contract Duration (Years), Group 2 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	6 years	6 years
Minimum [Member] | Contract Duration (Years), Group 3 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	11 years	11 years
Minimum [Member] | Contract Duration (Years), Group 4 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	16 years	16 years
Minimum [Member] | Contract Duration (Years), Group 5 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	20 years	20 years
Maximum [Member] | Contract Duration (Years), Group 1 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	5 years	5 years
Maximum [Member] | Contract Duration (Years), Group 2 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	10 years	10 years
Maximum [Member] | Contract Duration (Years), Group 3 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	15 years	15 years
Maximum [Member] | Contract Duration (Years), Group 4 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Contract duration (years)	20 years	20 years
Average [Member] | Contract Duration (Years), Group 1 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	1.76%	1.58%
Average partial withdrawal rates	3.30%	3.08%
Average [Member] | Contract Duration (Years), Group 2 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	6.59%	8.55%
Average partial withdrawal rates	3.30%	3.55%
Average [Member] | Contract Duration (Years), Group 3 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	11.25%	12.01%
Average partial withdrawal rates	3.32%	3.59%
Average [Member] | Contract Duration (Years), Group 4 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	12.03%	12.99%
Average partial withdrawal rates	3.18%	3.22%
Average [Member] | Contract Duration (Years), Group 5 [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Average lapse rates	11.68%	12.54%
Average partial withdrawal rates	3.18%	3.22%