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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Income
Net income available to common stockholders	$ 36,757	$ 41,113	$ 116,630	$ 117,426
Diluted net income per share	$ 36,757	$ 41,113	$ 116,630	$ 117,426
Weighted-Average Shares
Net income available to common stockholders (in shares)	51,433,227	49,286,945	50,085,701	49,244,403
Effect of potentially dilutive stock options and restricted stock awards (in shares)	136,330	205,074	141,679	213,782
Diluted net income per share (in shares)	51,569,557	49,492,019	50,227,380	49,458,185
Per Share Amount
Net income available to common stockholders (in dollars per share)	$ 0.71	$ 0.83	$ 2.33	$ 2.38
Diluted net income per share (in dollars per share)	$ 0.71	$ 0.83	$ 2.32	$ 2.37