Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Available-for-sale securities, amortized cost	$ 30,244,896	$ 13,894,348
Allowance for Credit Losses	392	0
Held-to-maturity securities	$ 17,216,871	$ 14,115,272
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	350,000	350,000
Preferred stock, shares outstanding	350,000	350,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares, issued	51,888,463	51,655,607
Common stock, shares outstanding	51,888,463	51,655,607