Goodwill and Other Intangible Assets - Summary of Other Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,142,166	$ 1,141,824
Accumulated Amortization	564,143	529,767
Net Carrying Amount	578,023	612,057
Domains Names Available for Sale [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	30,121	29,954
Accumulated Amortization	5,431	4,976
Net Carrying Amount	$ 24,690	$ 24,978
Weighted average useful life	Indefinite	Indefinite
Developed Technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 284,043	$ 284,005
Accumulated Amortization	119,810	111,348
Net Carrying Amount	$ 164,233	$ 172,657
Weighted average useful life	7 years	7 years	7 years
Subscriber Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 659,762	$ 659,662
Accumulated Amortization	366,163	345,070
Net Carrying Amount	$ 293,599	$ 314,592
Weighted average useful life	7 years	7 years
Trade-Names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 133,806	$ 133,805
Accumulated Amortization	61,280	57,789
Net Carrying Amount	$ 72,526	$ 76,016
Weighted average useful life	8 years	8 years
Intellectual Property
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 34,120	$ 34,084
Accumulated Amortization	11,145	10,270
Net Carrying Amount	$ 22,975	$ 23,814
Weighted average useful life	13 years	13 years
Leasehold Interests
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 314	$ 314
Accumulated Amortization	314	314
Net Carrying Amount	$ 0	$ 0
Weighted average useful life	1 year	1 year