Summary of Goodwill (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Beginning Balance	$ 1,284,079	[1]
Foreign currency translation adjustments	(134)
Ending Balance	1,283,945	[1]
U.S. Operating Segment
Goodwill [Line Items]
Beginning Balance	1,174,041	[1]
Ending Balance	1,174,041	[1]
International Operating Segment
Goodwill [Line Items]
Beginning Balance	110,038	[1]
Foreign currency translation adjustments	(134)
Ending Balance	$ 109,904	[1]

[1] Balances are presented net of accumulated impairment losses of $214,031 for the U.S. operating segment and $27,622 for the international operating segment.