Acquisitions (Details) NZD in Millions, AUD in Millions	1 Months Ended					3 Months Ended		9 Months Ended
	Apr. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 31, 2015 USD ($)	Oct. 31, 2015 AUD	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jan. 31, 2016 USD ($)	Jan. 31, 2016 NZD	Dec. 31, 2015 NZD
Business Acquisition [Line Items]
Goodwill acquired								$ 219,427,000
Mandatorily redeemable noncontrolling interests		$ 18,981,000				$ 0		0
Acquisition-related costs						1,400,000	$ 600,000	7,500,000	$ 1,000,000
RELS LLC [Member]
Business Acquisition [Line Items]
Ownership percentage in joint venture		50.10%										50.10%
Property Intelligence [Member]
Business Acquisition [Line Items]
Goodwill acquired								219,427,000
FNC, Inc. [Member]
Business Acquisition [Line Items]
Cash paid at closing in acquisition	$ 400,000,000
Contingent consideration	8,000,000
Deferred tax liability acquired	90,300,000
FNC, Inc. [Member] | Property Intelligence [Member]
Business Acquisition [Line Items]
Goodwill acquired	218,300,000							$ 218,300,000
Goodwill increase as a result of change in purchase price allocation						$ 6,800,000
FNC, Inc. [Member] | Property and equipment [Member]
Business Acquisition [Line Items]
Property and equipment acquired	$ 79,800,000
Estimated average life in years	12 years
FNC, Inc. [Member] | Client lists [Member]
Business Acquisition [Line Items]
Estimated average life in years	16 years
Finite-lived intangible assets acquired	$ 141,800,000
FNC, Inc. [Member] | Trade names [Member]
Business Acquisition [Line Items]
Estimated average life in years	19 years
Finite-lived intangible assets acquired	$ 15,900,000
FNC, Inc. [Member] | Non-compete agreements [Member]
Business Acquisition [Line Items]
Estimated average life in years	5 years
Finite-lived intangible assets acquired	$ 18,800,000
FNC, Inc. [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Estimated average life in years	10 years
Finite-lived intangible assets acquired	$ 2,900,000
FNC, Inc. [Member] | Maximum [Member]
Business Acquisition [Line Items]
Consideration transferred	475,000,000
Certain closing adjustments to be paid	$ 75,000,000
PIQ Acquisition [Member]
Business Acquisition [Line Items]
Remaining equity interest acquired										40.00%	40.00%
Mandatorily redeemable noncontrolling interests		$ 19,000,000								$ 19,000,000	NZD 27.8	NZD 27.8
RELS LLC [Member]
Business Acquisition [Line Items]
Cash paid at closing in acquisition		65,000,000
Property and equipment acquired		27,000,000
Goodwill acquired		23,100,000
Amount of goodwill deductible for tax purposes		11,500,000
Gain/(loss) on investments and other, net		$ 34,300,000
RELS LLC [Member] | Property and equipment [Member]
Business Acquisition [Line Items]
Estimated average life in years		10 years
RELS LLC [Member] | Client lists [Member]
Business Acquisition [Line Items]
Estimated average life in years		10 years
Finite-lived intangible assets acquired		$ 48,400,000
RELS LLC [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Estimated average life in years		10 years
Finite-lived intangible assets acquired		$ 5,000,000
Cordell Information Pty Ltd [Member]
Business Acquisition [Line Items]
Cash paid at closing in acquisition			$ 49,100,000	AUD 70.0
Property and equipment acquired			14,300,000
Goodwill acquired			$ 31,900,000
Cordell Information Pty Ltd [Member] | Property and equipment [Member]
Business Acquisition [Line Items]
Estimated average life in years			10 years	10 years
Cordell Information Pty Ltd [Member] | Client lists [Member]
Business Acquisition [Line Items]
Estimated average life in years			8 years	8 years
Finite-lived intangible assets acquired			$ 5,500,000
Cordell Information Pty Ltd [Member] | Trade names [Member]
Business Acquisition [Line Items]
Estimated average life in years			4 years	4 years
Finite-lived intangible assets acquired			$ 600,000
Landsafe [Member]
Business Acquisition [Line Items]
Cash paid at closing in acquisition					$ 122,000,000
Goodwill acquired					$ 64,600,000
Landsafe [Member] | Client lists [Member]
Business Acquisition [Line Items]
Estimated average life in years					10 years
Finite-lived intangible assets acquired					$ 53,400,000
Landsafe [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Estimated average life in years					10 years
Finite-lived intangible assets acquired					$ 4,300,000