Business Combinations - Additional Information (Detail) £ in Millions			7 Months Ended	12 Months Ended
	Jun. 01, 2015 USD ($)	Jun. 01, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill			$ 924,847,000	$ 924,847,000	$ 785,032,000
dlc [Member]
Business Acquisition [Line Items]
Business combination, aggregate purchase price	$ 274,700,000	£ 180.6
Goodwill	$ 66,486,000
Amount of goodwill expected to be tax deductible					$ 0
Revenue included in condensed consolidated statement of income			27,500,000
Net income included in condensed consolidated statement of income			$ 6,300,000
General and Administrative Expense [Member] | dlc [Member]
Business Acquisition [Line Items]
Acquisition and integration costs				$ 2,800,000