Interim Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Available-for-sale securities, cost	$ 14,414,219	$ 13,497,945
Held-to-maturity securities	$ 7,730,811	$ 7,415,656
Preferred stock, par value	$ 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	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares outstanding	51,461,496	50,924,925