Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic EPS [Abstract]
Weighted average common shares outstanding (in shares)	43,711,000	33,619,000	41,375,000	33,293,000
Net income available to common shareholders	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Basic EPS (in dollars per share)	$ 0.44	$ 0.43	$ 1.06	$ 1.24
Diluted EPS [Abstract]
Weighted average common shares outstanding (in shares)	43,711,000	33,619,000	41,375,000	33,293,000
Dilutive effect of common stock option and restricted stock (in shares)	424,000	342,000	394,000	333,000
Weighted average common shares and common share equivalent (in shares)	44,135,000	33,961,000	41,769,000	33,626,000
Net income available to common shareholders	$ 19,257	$ 14,535	$ 43,822	$ 41,442
Diluted EPS (in dollars per share)	$ 0.44	$ 0.43	$ 1.05	$ 1.23
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options excluded from calculation of diluted EPS (in shares)	972,403	1,176,670	1,157,135	1,197,417