Acquisitions (MSB/DQ Purchase Price Allocation) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 2,107,255	$ 1,881,547	$ 1,780,758
Property Intelligence [Member]
Business Acquisition [Line Items]
Goodwill	$ 1,188,788	$ 963,080	$ 957,329
Property Intelligence [Member] | MSB/Data Quick [Member]
Business Acquisition [Line Items]
Cash and cash equivalents				$ 36
Accounts receivable				9,227
Prepaid expenses and other current assets				2,190
Deferred income tax assets, current				6,658
Property and equipment				177,311
Goodwill				307,773
Other intangible assets				129,400
Deferred income tax, net of current				29,760
Investment in affiliates				18,300
Total assets acquired				680,655
Accounts payable and accrued expenses				3,911
Income taxes payable				31
Deferred revenue, current				22,371
Deferred revenue, net of current				1,823
Net assets acquired				$ 652,519