Offsetting Assets and Liabilities - Offsetting Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivative Asset [Abstract]
Collateral Received	$ (800)	$ (1,500)
Consolidated VIEs [Member]
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	4,997
Gross Amounts Offset in the Statement of Financial Position	0
Net Amounts of Assets Presented in the Statement of Financial Position	4,997
Financial Instruments	0
Collateral Received	(461)
Net Amount	4,536
Securities Borrowed [Member]
Securities Borrowed [Abstract]
Gross Amounts of Recognized Assets	82,814	75,274
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	82,814	75,274
Financial Instruments	0	0
Collateral Received	(82,814)	(75,274)
Net Amount	0	0
Derivatives [Member]
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	8,413	12,588
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	8,413	12,588
Financial Instruments	0	0
Collateral Received	(810)	(1,518)
Net Amount	7,603	11,070
Exchange Traded Options [Member] | Long [Member]
Derivative Asset [Abstract]
Gross Amounts of Recognized Assets	3,106	5,910
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	3,106	5,910
Financial Instruments	0	0
Collateral Received	0	0
Net Amount	$ 3,106	$ 5,910