Net Income Per Share - Reconciliation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net Income	$ 17,067	$ 16,122	$ 51,207	$ 44,902
Diluted net income per share	$ 17,067	$ 16,122	$ 51,207	$ 44,902
Net income available to common stockholders (in shares)	37,850,827	36,054,867	37,785,236	36,013,049
Effect of dilutive stock options and warrants (in shares)	267,372	274,114	268,750	282,337
Net income available to common stockholders (in shares)	38,118,199	36,328,981	38,053,986	36,295,386
Net income available to common stockholders (in dollars per share)	$ 0.46	$ 0.45	$ 1.36	$ 1.25
Net income available to common stockholders (in dollars per share)	$ 0.45	$ 0.45	$ 1.35	$ 1.24