Recent Accounting Pronouncements - Impact of Adoption of ASC 606 on Financial Statements - Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,264,958	$ 1,124,100	$ 3,612,463	$ 3,297,774
Costs of revenue:
Direct costs	824,024	728,444	2,397,633	2,195,282
Indirect costs and selling expenses	324,828	273,145	859,262	788,569
Depreciation and amortization	21,198	17,717	58,797	53,563
Total costs of revenue	1,170,050	1,019,306	3,315,692	3,037,414
Income from operations	94,908	104,794	296,771	260,360
Interest expense and other, net	13,466	10,566	31,773	32,769
Income before taxes	81,442	94,228	264,998	227,591
Income tax expense (benefit)	13,297	29,729	49,424	(21,749)
Net income	$ 68,145	$ 64,499	$ 215,574	$ 249,340
Basic earnings per share	$ 2.74	$ 2.62	$ 8.69	$ 10.14
Diluted earnings per share	$ 2.69	$ 2.56	$ 8.50	$ 9.88
Under ASC 605
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,263,174		$ 3,599,511
Costs of revenue:
Direct costs	824,024		2,397,633
Indirect costs and selling expenses	324,597		860,294
Depreciation and amortization	21,198		58,797
Total costs of revenue	1,169,819		3,316,724
Income from operations	93,355		282,787
Interest expense and other, net	13,466		31,773
Income before taxes	79,889		251,014
Income tax expense (benefit)	12,875		45,820
Net income	$ 67,014		$ 205,194
Basic earnings per share	$ 2.70		$ 8.27
Diluted earnings per share	$ 2.64		$ 8.09
ASU 2014-09 | Effect of ASC 606
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,784		$ 12,952
Costs of revenue:
Indirect costs and selling expenses	231		(1,032)
Total costs of revenue	231		(1,032)
Income from operations	1,553		13,984
Income before taxes	1,553		13,984
Income tax expense (benefit)	422		3,604
Net income	$ 1,131		$ 10,380
Basic earnings per share	$ 0.05		$ 0.42
Diluted earnings per share	$ 0.04		$ 0.41