Investments - Offsetting of Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Asset derivatives:
Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets	$ 10,685	$ 2,647
Free-standing derivatives
Asset derivatives:
Gross Amounts	10,685	2,647
Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets	10,685	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	10,338	1,868
Net Amount	$ 347	$ 779