Acquisitions - Acquisition of Recommind, Inc. (Details) - USD ($)	Jul. 20, 2016	Dec. 31, 2017	Jun. 30, 2017
Purchase Price Allocation
Goodwill		$ 3,578,976,000	$ 3,416,749,000
Recommind Inc
Business Acquisition [Line Items]
Purchase consideration	$ 170,100,000
Purchase Price Allocation
Current assets	30,034,000
Non-current tangible assets	1,245,000
Long-term deferred tax liabilities	(1,780,000)
Other liabilities assumed	(27,497,000)
Total identifiable net assets	78,702,000
Goodwill	91,405,000
Net assets acquired	170,107,000
Goodwill expected to be tax deductible	0
Acquired receivables, fair value	28,700,000
Acquired receivables, gross contractual amount	29,600,000
Acquired receivables, estimated uncollectible	900,000
Recommind Inc | Customer assets
Purchase Price Allocation
Acquired intangible assets	51,900,000
Recommind Inc | Technology assets
Purchase Price Allocation
Acquired intangible assets	$ 24,800,000