Investments (Impaired Mortgage Loans) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		$ 2,758	$ 16,931
Impaired Financing Receivable, Recorded Investment		2,216	16,421
Impaired Financing Receivable, Related Allowance		0	588
Impaired Financing Receivable Net Of Related Allowance		2,216	15,833
Impaired Financing Receivable, Average Recorded Investment	[1]	2,249	17,625	$ 27,054
Impaired Financing Receivable, Interest Income, Accrual Method		142	1,100	1,284
Impaired mortgage loans with no valuation allowance recorded
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		2,758	4,033
Impaired Financing Receivable, Recorded Investment		2,216	4,033
Impaired Financing Receivable, Related Allowance		0	0
Impaired Financing Receivable Net Of Related Allowance		2,216	4,033
Impaired Financing Receivable, Average Recorded Investment	[1]	2,249	6,033	13,227
Impaired Financing Receivable, Interest Income, Accrual Method		142	330	647
Impaired mortgage loans with valuation allowance recorded
Financing Receivable, Impaired [Line Items]
Impaired Financing Receivable, Unpaid Principal Balance		0	12,898
Impaired Financing Receivable, Recorded Investment		0	12,388
Impaired Financing Receivable, Related Allowance		0	588
Impaired Financing Receivable Net Of Related Allowance		0	11,800
Impaired Financing Receivable, Average Recorded Investment	[1]	0	11,592	13,827
Impaired Financing Receivable, Interest Income, Accrual Method		$ 0	$ 770	$ 637

[1] Average recorded investment represents the average loan balances as of the beginning of period and all subsequent quarterly end of period balances.