Interim Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Available-for-sale securities, cost	$ 12,053,305	$ 12,588,783
Held-to-maturity securities	$ 9,910,504	$ 8,376,138
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	52,684,159	52,254,074