Interim Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value, in usd per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value, in usd per share	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares outstanding	52,922,219	52,835,188
Available-for-sale securities, cost	$ 10,189,071	$ 11,131,008
Held-to-maturity securities	$ 14,229,439	$ 12,548,280