Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 22,678	$ 13,291
Weighted average shares outstanding - basic (in shares)	62,242,183	62,078,404
Dilutive securities outstanding (in shares)	762,601	604,583
Weighted average shares outstanding - diluted (in shares)	63,004,784	62,682,987
Earnings per share - basic (in dollars per share)	$ 0.36	$ 0.21
Earnings per share - diluted (in dollars per share)	$ 0.36	$ 0.21
Weighted Average antidilutive securities outstanding (in shares)	19,610	17,050
Stock options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average antidilutive securities outstanding (in shares)	18,315	15,191
Restricted shares [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average antidilutive securities outstanding (in shares)	1,295	1,859