Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Amortized cost	$ 2,797,990	$ 2,344,174
Fair Value, Held-to-maturity	$ 1,085,481	$ 604,223
Common stock, par value	$ 0	$ 0
Common stock, authorized	225,000,000	225,000,000
Common stock, shares issued	135,919,625	135,600,501
Common stock, shares outstanding	135,919,625	135,600,501