Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Statement Of Financial Position [Abstract]
Securities held to maturity, fair value	$ 1,181,652	$ 1,143,213
Unearned income on loans	$ 52,598	$ 51,661
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	145,913,917	140,314,846
Treasury stock, shares	650,482	385,604