Investments - Impairment Charges in Earnings on Available-for-sale Securities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Impairment charges recognized in earnings	$ 478	$ 1,564	$ 3,308	$ 2,433
Equity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Impairment charges recognized in earnings	10	275	42	351
Investments in fixed-maturity securities not in default [Member] | Fixed-maturity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Impairment charges recognized in earnings	466	1,287	3,145	2,075
Investments in fixed-maturity securities in default [Member] | Fixed-maturity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Impairment charges recognized in earnings	$ 2	$ 2	$ 121	$ 7