Income Taxes Reconciliation of Expected Federal Tax Expense to Actual (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Expected Tax Expense									$ (1,045)	$ 1,919	$ (680)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent									35.00%	35.00%	35.00%
Release of Tax Valuation Allowance in Other Comprehensive Income									$ 0	$ 0	$ (42)
Effective Income Tax Rate Reconciliation, Release of Valuation Allowance Previously in Other Comprehensive Income, Percent									0.00%	0.00%	2.20%
Taxable Intercompany Stock Sales									$ 0	$ 263	$ 0
Effective Income Tax Rate Reconciliation, Taxable Intercompany Stock Sales, Percent									0.00%	4.80%	0.00%
Tax Exempt Interest and Dividends-Received Deductions									$ (360)	$ (553)	$ (746)
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent									12.10%	(10.10%)	38.40%
Adjustment of Prior Year Income Taxes									$ 68	$ 29	$ (317)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Percent									(2.30%)	0.50%	16.30%
Tax Effect of Graduated Income Tax Rates									$ (140)	$ (57)	$ (71)
Effective Income Tax Rate Reconciliation, Effect of Graduate Rates, Percent									4.70%	(1.00%)	3.70%
Unrecognized Tax Benefits, Income Tax Penalties Expense									$ (355)	$ 1,672	$ 1,890
Effective Income Tax Rate Reconciliation, Tax Contingency, Domestic, Percent									11.90%	30.50%	(97.30%)
Tax Benefit not Recognized due to Non-Deductibility of Tax Compliance Issue									$ (384)	$ 241	$ 1,152
Effective Income Tax Rate Reconciliation, Nondeductible Costs to Remediate Tax Compliance Issue, Percent									12.90%	4.40%	(59.30%)
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount									$ 35,718	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent									(1196.20%)	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount									$ 1,621	$ 0	$ 0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Percent									(54.30%)	0.00%	0.00%
Other Reconciling Items									$ 18	$ 0	$ 14
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent									(0.70%)	0.00%	(0.80%)
Federal income tax expense	$ 35,069	$ (339)	$ 1,524	$ (1,113)	$ (490)	$ 1,845	$ 1,077	$ 1,082	$ 35,141	$ 3,514	$ 1,200
Effective Income Tax Rate Reconciliation, Percent									(1176.90%)	64.10%	(61.80%)