Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Tax effect	$ 1,288	$ 1,514
Net-of-tax amount	(3,875)	(2,446)
Net unrealized loss on available-for-sale securities [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net unrealized gain (loss)	(3,398)	(1,141)
Net unrealized loss on derivatives used for cash flow hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Net unrealized gain (loss)	$ (1,765)	$ (2,819)