Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Significant Accounting Policies - Investment in Marketable Securities (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2018	Dec. 31, 2017
Investment in Marketable Securities
Marketable securities		$ 28,252,000	$ 28,579,000
Proceeds from sale of marketable securities	$ 54,400,000
Marketable Securities, Realized Gain (Loss)	$ 3,300,000
Fair Value
Investment in Marketable Securities
Marketable securities		28,252,000	28,579,000
Equity marketable securities
Investment in Marketable Securities
Cost basis		0	0
Commercial mortgage-backed securities
Investment in Marketable Securities
Marketable securities		28,252,000	28,579,000
Cost basis		$ 27,500,000	$ 27,500,000