Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Preferred stock, authorized shares	4,400,000	4,400,000
Common stock, authorized shares	350,000,000	350,000,000
Common stock, issued shares	204,543,707	204,417,093
Common stock, outstanding shares	204,543,707	204,417,093
Estimate of Fair Value Measurement [Member]
Held-to-maturity, fair value	$ 636,484	$ 552,088