Earnings per Share (Reconciliation between Basic and Diluted Earnings per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income for basic and diluted earnings per share	$ 13,143	$ 18,072	$ 44,029	$ 51,824
Basic weighted average shares outstanding	37,919	37,214	37,435	36,859
Dilutive effect of stock options and restricted stock awards	532	1,906	1,241	2,299
Diluted weighted average shares outstanding	38,451	39,120	38,676	39,158
Basic earnings per common share	$ 0.35	$ 0.49	$ 1.18	$ 1.41
Diluted earnings per common share	$ 0.34	$ 0.46	$ 1.14	$ 1.32