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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Income
Net income available to common stockholders	$ 24,358	$ 21,059	$ 71,687	$ 58,758
Diluted net income per share	$ 24,358	$ 21,059	$ 71,687	$ 58,758
Weighted-Average Shares
Net income available to common stockholders (in shares)	48,431,880	40,779,423	43,845,675	40,740,714
Effect of potentially dilutive stock options and restricted stock awards (in shares)	211,894	246,361	217,544	229,501
Diluted net income per share (in shares)	48,643,774	41,025,784	44,063,219	40,970,215
Per Share Amount
Net income available to common stockholders (in dollars per share)	$ 0.50	$ 0.51	$ 1.64	$ 1.44
Diluted net income per share (in dollars per share)	$ 0.50	$ 0.51	$ 1.63	$ 1.43