Fair Value Measurements and Fair Value of Financial Instruments (Details) - Schedule of fair value on recurring item basis - Recurring [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fair value	$ 528,871	$ 424,653
Municipal Securities [Member]
Fair value	$ 9,311	$ 9,377
Valuation Techniques	Discounted cash flows	Discounted cash flows
Unobservable Input	Discount rate	Discount rate
Range	2.90%	2.90%