Income Taxes Income Taxes - Additional Information (Details)	6 Months Ended
Jun. 30, 2018
Valuation Allowance [Abstract]
Valuation Allowance, Commentary	The Company believes it is more likely than not that all deferred tax assets will be fully realized. In assessing the need for a valuation allowance, management considered future taxable temporary difference reversals, future taxable income exclusive of reversing temporary differences and carryovers, taxable income in open carry back years and other tax planning strategies. From time to time, tax planning strategies could include holding a portion of debt securities with market value losses until recovery, making investments which have specific tax characteristics and business considerations such as asset-liability matching.

Describes the facts and circumstances that resulted in an assessment that it is more likely than not that all or a portion of that deferred tax asset will not be realized. Includes in this description the following: (1) the amount of taxable income and the periods over which it must be earned to allow for the realization of the deferred tax asset; (2) actual levels of past taxable income; (3) reasons for significant differences in actual levels of past taxable income and pretax book income; and (4) known trends, events or transactions that are expected to affect future levels of taxable income.

No definition available.

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