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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net Income
Net income available to common stockholders	$ 21,059	$ 17,067	$ 58,758	$ 51,207
Diluted net income per share	$ 21,059	$ 17,067	$ 58,758	$ 51,207
Weighted-Average Shares
Net income available to common stockholders (in shares)	40,779,423	37,850,827	40,740,714	37,785,236
Effect of dilutive stock options and warrants (in shares)	246,361	267,372	229,501	268,750
Diluted net income per share (in shares)	41,025,784	38,118,199	40,970,215	38,053,986
Per Share Amount
Net income available to common stockholders (in dollars per share)	$ 0.51	$ 0.46	$ 1.44	$ 1.36
Diluted net income per share (in dollars per share)	$ 0.51	$ 0.45	$ 1.43	$ 1.35