Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Amortized cost	$ 2,181,478	$ 2,337,715
Fair Value, Held-to-maturity	$ 743,481	$ 853,039
Common stock, par value
Common stock, authorized	225,000,000	225,000,000
Common stock, shares issued	107,946,952	106,384,982
Common stock, shares outstanding	107,946,952	106,384,982