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
Summary of earnings per share
Net income	$ 14,655	$ 11,601	$ 39,665	$ 32,658
Weighted Average Shares (in shares)
BASIC SHARES	22,946,308	21,654,188	22,886,521	21,613,157
EFFECT OF DILUTIVE SECURITIES	100,806	52,116	72,799	31,300
DILUTIVE SHARES	23,047,114	21,706,304	22,959,320	21,644,457
NET INCOME PER SHARE (in dollars per share)
BASIC EPS	$ 0.64	$ 0.54	$ 1.73	$ 1.51
EFFECT OF DILUTIVE SECURITIES		$ (0.01)
DILUTIVE EPS	$ 0.64	$ 0.53	$ 1.73	$ 1.51