Investments - Offsetting of Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Asset derivatives:
Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets	$ 7,643	$ 2,647
Free-standing derivatives
Asset derivatives:
Gross Amounts	7,643	2,647
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets	7,643	2,647
Gross Amounts Not Offset in the Consolidated Balance Sheets, Financial Instruments	0	0
Gross Amounts Not Offset in the Consolidated Balance Sheets, Cash Collateral Received	6,938	1,868
Net Amount	$ 705	$ 779

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