Fair Value of Financial Instruments (Level 3 Securities) (Details) - Recurring - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 14,836	$ 15,098
Net unrealized gains (losses)	228	168
Purchases		145
Disposals	(4,714)	(5,061)
Ending Balance	10,350	10,350
States, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	168	168
Net unrealized gains (losses)	(6)	(6)
Purchases		0
Disposals	(85)	(85)
Ending Balance	77	77
Corporate bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	9,494	9,894
Net unrealized gains (losses)	68	1
Purchases		0
Disposals	(506)	(839)
Ending Balance	9,056	9,056
Asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	456	449
Net unrealized gains (losses)	166	173
Purchases		0
Disposals	0	0
Ending Balance	622	622
Equities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4,718	4,587
Net unrealized gains (losses)	0	0
Purchases		145
Disposals	(4,123)	(4,137)
Ending Balance	$ 595	$ 595