Business Acquisitions (Summary of Preliminary Allocation of Purchase Consideration) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Jun. 30, 2017	Sep. 30, 2016	Aug. 16, 2016
Business Acquisition [Line Items]
Number of Years in Measurement Period from Acquisition Date to Change Underlying Assumptions		1 year
Allocation of the purchase consideration:
Cash				$ 137
Accounts receivable(b)				14,897
Goodwill				117,178
Identifiable intangible assets(c)				110,800
Other assets				1,521
Total assets acquired				244,533
Current liabilities				4,134
Deferred tax liability				19,515
Deferred revenue				2,784
Other long term liabilities				634
Total liabilities assumed				27,067
Net assets acquired				217,466
Closing market value of common stock		$ 17.41
Intangible Assets Acquired				$ 110,800
TouchCommerce, Inc. [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 217,466
Allocation of the purchase consideration:
Stock Issued During Period, Shares, Acquisitions	5,749,807
Closing market value of common stock				$ 14.78
TouchCommerce, Inc. [Member] | Cash Distribution [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 113,008
TouchCommerce, Inc. [Member] | Share Distribution [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	85,000
TouchCommerce, Inc. [Member] | Contingent and deferred acquisition payment [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 19,458
Other Acquisitions [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 97,200	$ 50,400
Allocation of the purchase consideration:
Stock Issued During Period, Shares, Acquisitions		844,108
Other Acquisitions [Member] | Share Distribution [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 13,400
Other Acquisitions [Member] | Contingent Consideration Payments [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 8,300
Technology-Based Intangible Assets [Member]
Allocation of the purchase consideration:
Intangible Assets Acquired				$ 26,000
Weighted Average Useful Life, Intangible Assets Acquired	6 years
Customer Relationships [Member]
Allocation of the purchase consideration:
Intangible Assets Acquired				81,600
Weighted Average Useful Life, Intangible Assets Acquired	10 years
Trade Names [Member]
Allocation of the purchase consideration:
Intangible Assets Acquired				$ 3,200
Weighted Average Useful Life, Intangible Assets Acquired	5 years