Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Securities held to maturity, fair value	$ 1,240,956	$ 952,033
Unearned income on loans	$ 52,114	$ 47,110
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	140,080,637	127,436,261
Treasury stock, shares	371,335	215,502