Investments (Cumulative Noncredit Portion of Other Than Temporary Impairment Recognized in Other Comprehensive Income and Change in Fair Value Since Other Than Temporary Impairment) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Amortized cost	$ 416,967	$ 481,421
OTTI recognized in other comprehensive income	(177,039)	(178,824)
Change in fair value since OTTI was recognized	215,296	198,605
Fair value	455,224	501,202
Fixed Maturity Securities [Member] | Corporate Securities [Member]
Investment Holdings [Line Items]
Amortized cost	12,930	6,396
OTTI recognized in other comprehensive income	(5,112)	(2,975)
Change in fair value since OTTI was recognized	9,729	9
Fair value	17,547	3,430
Fixed Maturity Securities [Member] | Residential Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	392,598	466,871
OTTI recognized in other comprehensive income	(170,284)	(170,724)
Change in fair value since OTTI was recognized	206,943	199,149
Fair value	429,257	495,296
Fixed Maturity Securities [Member] | Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	6,585
OTTI recognized in other comprehensive income	0
Change in fair value since OTTI was recognized	190
Fair value	6,775
Fixed Maturity Securities [Member] | Other Asset Backed Securities [Member]
Investment Holdings [Line Items]
Amortized cost	4,854	8,154
OTTI recognized in other comprehensive income	(1,643)	(5,125)
Change in fair value since OTTI was recognized	(1,566)	(553)
Fair value	$ 1,645	$ 2,476