Net income Per Share - Reconciliation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Net income available to common stockholders	$ 53,479	$ 39,577	$ 90,305	$ 62,239
Basic weighted-average shares outstanding	43,471	44,671	43,787	44,772
Dilutive effect of potential common stock equivalents — restricted stock units	192	301	193	317
Diluted weighted-average shares outstanding	43,663	44,972	43,980	45,089
Earnings per common share:
Basic	$ 1.23	$ 0.89	$ 2.06	$ 1.39
Diluted	$ 1.22	$ 0.88	$ 2.05	$ 1.38