Fair Value Disclosures - Level 3 Roll Forward (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Net Asset (Liability) Value [Roll Forward]
Beginning balance	$ 30,907	$ 0
Purchases/additions	(272)	2,293
Sales	0	0
Payments received	(102)	(32)
Premium amortization, net	0	0
(Decrease) increase in value	(106)	(43)
Ending balance	30,427	2,218
Derivative Financial Instruments, Liabilities [Member] | Credit Risk Contract [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(9)	0
Purchases/additions	(272)	(20)
Sales	0	0
Payments received	0	0
Premium amortization, net	0	0
(Decrease) increase in value	149	4
Ending balance	(132)	(16)
Corporate Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	28,778
Purchases/additions	0
Sales	0
Payments received	0
Premium amortization, net	0
(Decrease) increase in value	(233)
Ending balance	28,545
Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	2,138	0
Purchases/additions	0	2,313
Sales	0	0
Payments received	(102)	(32)
Premium amortization, net	0	0
(Decrease) increase in value	(22)	(47)
Ending balance	$ 2,014	$ 2,234