Net Income Per Share and Stockholders' Equity - Summary of Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
NET INCOME PER SHARE—BASIC:
Net income attributable to ADS	$ 15,812	$ 32,105	$ 76,762	$ 67,710
Dividends to redeemable convertible preferred stockholders	(467)	(456)	(1,442)	(1,415)
Dividends paid to unvested restricted stockholders	(25)	(12)	(55)	(47)
Net income available to common stockholders and participating securities	15,320	31,637	75,265	66,248
Undistributed income allocated to participating securities	(1,027)	(2,766)	(6,048)	(5,588)
Net income available to common stockholders – Basic	$ 14,293	$ 28,871	$ 69,217	$ 60,660
Weighted average number of common shares outstanding – Basic	57,180	55,917	56,925	55,497
Net income per common share – Basic	$ 0.25	$ 0.52	$ 1.22	$ 1.09
NET INCOME PER SHARE—DILUTED:
Net income available to common stockholders – Diluted	$ 14,293	$ 28,871	$ 69,217	$ 60,660
Weighted average number of common shares outstanding – Basic	57,180	55,917	56,925	55,497
Assumed exercise of stock options	505	542	557	627
Weighted average number of common shares outstanding – Diluted	57,685	56,459	57,482	56,124
Net income per common share – Diluted	$ 0.25	$ 0.51	$ 1.20	$ 1.08
Potentially dilutive securities excluded as anti-dilutive	6,079	6,060	6,068	6,252