CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended									12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	[1]	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue	$ 1,373,878	$ 1,264,958	$ 1,181,641	$ 1,165,864	$ 1,170,086	$ 1,124,100	$ 1,087,860		$ 1,085,814	$ 4,986,341	$ 4,467,860	$ 4,354,617
Costs of revenue:
Direct costs										3,304,053	2,978,608	2,934,804
Indirect costs and selling expenses										1,218,544	1,076,356	1,050,792
Depreciation and amortization										85,877	72,196	71,760
Total costs of revenue										4,608,474	4,127,160	4,057,356
Income from operations	81,096	94,908	102,263	99,600	80,340	104,794	88,262		67,304	377,867	340,700	297,261
Interest expense and other, net										49,958	42,036	48,642
Income before income taxes										327,909	298,664	248,619
Income tax (benefit) expense										62,305	(2,507)	84,948
Net income	$ 50,030	$ 68,145	$ 68,596	$ 78,833	$ 51,831	$ 64,499	$ 142,795		$ 42,046	$ 265,604	$ 301,171	$ 163,671
Basic earnings per share	$ 2.01	$ 2.74	$ 2.76	$ 3.19	$ 2.10	$ 2.62	$ 5.80		$ 1.72	$ 10.70	$ 12.23	$ 6.71
Diluted earnings per share	$ 1.96	$ 2.69	$ 2.71	$ 3.10	$ 2.05	$ 2.56	$ 5.66		$ 1.67	$ 10.46	$ 11.93	$ 6.53
Weighted-average basic shares outstanding	24,875	24,866	24,856	24,737	24,700	24,656	24,622		24,487	24,833	24,616	24,401
Weighted-average diluted shares outstanding	25,472	25,348	25,338	25,424	25,331	25,234	25,211		25,243	25,395	25,255	25,069

[1] Net income for the second quarter of FY2019 includes a net benefit related to the TCJA. See Note 19.