Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets
Securities held to maturity, fair value	$ 1,195,367	$ 1,182,846
Shareholders' Equity
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock, authorized (in shares)	250,000,000	250,000,000
Common stock, issued (in shares)	67,559,128	67,481,992
Common stock, outstanding (in shares)	67,559,128	67,481,992