Stockholders' Equity (Details 3) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Amounts Reclassified from AOCI
Realized gain on sale of securities	$ 7,429	$ 5,889	$ 16,246	$ 15,597
Net Income Available to Common Stock and Participating Securities	66,645	76,185	146,290	150,495
Total reclassifications for period	(5,178)	(6,274)	(15,458)	(16,634)
Accumulated Other Comprehensive Income/(Loss)
Unrealized losses recorded in AOCI on securities for which Other-than-temporary impairments had been recognized in earnings in prior periods	0		0		$ 0
Amounts Reclassified from AOCI \| Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest
Amounts Reclassified from AOCI
Realized gain on sale of securities	(5,178)	(5,656)	(15,458)	(15,602)
OTTI recognized in earnings		(618)		(1,032)
Net Income Available to Common Stock and Participating Securities	$ (5,178)	$ (6,274)	$ (15,458)	$ (16,634)

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Total of accumulated other comprehensive loss related to that portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized either as available-for-sale or held-to-maturity that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading). Excludes other-than-temporary impairment (OTTI).

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Amount after tax of income (loss) from continuing operations including portion attributable to the noncontrolling interest.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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