Significant Accounting Policies and Pronouncements (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Accounting Policies [Abstract]
Commercial mortgage and other loans, Loan-to- value ratios (greater than)	100.00%
Commercial mortgage and other loans, Loan-to-value ratios (less than)	100.00%
Commercial mortgage and other loans, Debt service coverage ratios (less than)	1.0
Commercial mortgage and other loans, Debt service coverage ratios (greater than)	1.0
Change in Accounting Estimate [Line Items]
Securities Loaned Transactions Collateral Fair Value of Domestic Securities	102.00%
Securities Loaned Transactions Collateral Fair Value of Foreign Securities	105.00%
Uncertain tax positions measurement percentage (greater than)	50.00%
Minimum
Change in Accounting Estimate [Line Items]
Repurchase and Resale Agreements, Collateral, Percentage	95.00%
Insurance revenue and expense recognition, Assumed interest rate	0.00%	0.00%
Maximum
Change in Accounting Estimate [Line Items]
Insurance revenue and expense recognition, Assumed interest rate	8.30%	8.30%
Accumulated Other Comprehensive Income (loss)
Change in Accounting Estimate [Line Items]
Cumulative effect of adoption			$ (36,700)
Accumulated Other Comprehensive Income (loss) | ASU 2018-02
Change in Accounting Estimate [Line Items]
Cumulative effect of adoption	$ (36,714)		(36,714)
Accumulated Other Comprehensive Income (loss) | ASU 2016-01
Change in Accounting Estimate [Line Items]
Cumulative effect of adoption	$ (3)		(3)
Retained earnings
Change in Accounting Estimate [Line Items]
Cumulative effect of adoption			36,700
Retained earnings | ASU 2018-02
Change in Accounting Estimate [Line Items]
Cumulative effect of adoption			36,714
Retained earnings | ASU 2016-01
Change in Accounting Estimate [Line Items]
Cumulative effect of adoption			$ 337