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
	Sep. 30, 2018	Sep. 30, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,165,864	$ 1,085,814
Costs of revenue:
Direct costs	782,760	739,678
Indirect costs and selling expenses	264,757	261,244
Depreciation and amortization	18,747	17,588
Total costs of revenue	1,066,264	1,018,510
Income from operations	99,600	67,304
Interest expense and other, net	8,886	11,247
Income before taxes	90,714	56,057
Income tax expense (benefit)	11,881	14,011
Net income	$ 78,833	$ 42,046
Basic earnings per share	$ 3.19	$ 1.72
Diluted earnings per share	$ 3.10	$ 1.67
Under ASC 605
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,158,702
Costs of revenue:
Direct costs	782,760
Indirect costs and selling expenses	264,700
Depreciation and amortization	18,747
Total costs of revenue	1,066,207
Income from operations	92,495
Interest expense and other, net	8,886
Income before taxes	83,609
Income tax expense (benefit)	10,087
Net income	$ 73,522
Basic earnings per share	$ 2.97
Diluted earnings per share	$ 2.89
ASU 2014-09 | Effect of ASC 606
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 7,162
Costs of revenue:
Indirect costs and selling expenses	57
Total costs of revenue	57
Income from operations	7,105
Income before taxes	7,105
Income tax expense (benefit)	1,794
Net income	$ 5,311
Basic earnings per share	$ 0.21
Diluted earnings per share	$ 0.21