Segment Information (Financial Information) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Operating revenue	$ 474,914	$ 523,896	$ 500,204	$ 453,543	$ 390,886	$ 386,439	$ 386,013	$ 364,772	$ 1,952,557	$ 1,528,110	$ 1,405,040
Depreciation and amortization									172,578	150,377	143,364
Operating Income/(Loss)	56,939	84,824	75,515	57,311	27,032	65,920	60,707	49,265	274,589	202,924	169,758
Equity in earnings/(loss) of affiliates, net of tax	(99)	$ 607	$ 78	$ (90)	1,789	$ 3,498	$ 4,667	$ 3,766	496	13,720	14,120
Net Income/(Loss) from Continuing Operations									109,946	129,552	91,008
Capital Expenditures									80,718	80,558	87,154
Statement of Financial Position [Abstract]
Investments in affiliates, net	40,809				69,205				40,809	69,205
Long-Lived Assets	3,515,647				3,131,450				3,515,647	3,131,450
Total assets	3,907,534				3,673,716				3,907,534	3,673,716
Segment Reporting Information, Assets (Excluding Discontinued Operations Assets)	3,906,872				3,673,035				3,906,872	3,673,035
Domestic [Member]
Income Statement [Abstract]
Operating revenue									1,806,099	1,397,394	1,263,950
Statement of Financial Position [Abstract]
Segment Reporting Information, Assets (Excluding Discontinued Operations Assets)	3,198,197				2,811,160				3,198,197	2,811,160
Foreign [Member]
Income Statement [Abstract]
Operating revenue									146,458	130,716	141,090
Statement of Financial Position [Abstract]
Segment Reporting Information, Assets (Excluding Discontinued Operations Assets)	317,450				320,290				317,450	320,290
Operating Segments [Member] | Property Intelligence [Member]
Income Statement [Abstract]
Operating revenue									1,053,544	663,344	598,113
Depreciation and amortization									126,367	96,766	95,049
Operating Income/(Loss)									101,272	72,761	70,181
Equity in earnings/(loss) of affiliates, net of tax									1,588	22,622	22,949
Net Income/(Loss) from Continuing Operations									90,119	94,522	100,070
Capital Expenditures									49,900	48,902	48,535
Statement of Financial Position [Abstract]
Investments in affiliates, net	35,810				61,765				35,810	61,765
Long-Lived Assets	2,265,094				1,856,410				2,265,094	1,856,410
Total assets	2,429,167				2,058,412				2,429,167	2,058,412
Operating Segments [Member] | Property Intelligence [Member] | Domestic [Member]
Income Statement [Abstract]
Operating revenue									907,133	535,405	460,370
Statement of Financial Position [Abstract]
Long-Lived Assets	1,947,648				1,536,133				1,947,648	1,536,133
Operating Segments [Member] | Property Intelligence [Member] | Foreign [Member]
Income Statement [Abstract]
Operating revenue									146,411	127,939	137,743
Statement of Financial Position [Abstract]
Long-Lived Assets	317,446				320,277				317,446	320,277
Operating Segments [Member] | Risk Management and Work Flow [Member]
Income Statement [Abstract]
Operating revenue									909,100	875,057	816,717
Depreciation and amortization									28,652	37,493	34,253
Operating Income/(Loss)									252,998	216,178	166,640
Equity in earnings/(loss) of affiliates, net of tax									0	0	0
Net Income/(Loss) from Continuing Operations									252,997	216,147	166,631
Capital Expenditures									12,268	12,714	16,184
Statement of Financial Position [Abstract]
Investments in affiliates, net	0				0				0	0
Long-Lived Assets	1,165,369				1,183,318				1,165,369	1,183,318
Total assets	1,328,008				1,316,785				1,328,008	1,316,785
Operating Segments [Member] | Risk Management and Work Flow [Member] | Domestic [Member]
Income Statement [Abstract]
Operating revenue									909,065	872,319	813,401
Statement of Financial Position [Abstract]
Long-Lived Assets	1,165,369				1,183,305				1,165,369	1,183,305
Operating Segments [Member] | Risk Management and Work Flow [Member] | Foreign [Member]
Income Statement [Abstract]
Operating revenue									35	2,738	3,316
Statement of Financial Position [Abstract]
Long-Lived Assets	0				13				0	13
Corporate [Member]
Income Statement [Abstract]
Operating revenue									12	39	31
Depreciation and amortization									17,559	16,118	14,062
Operating Income/(Loss)									(79,681)	(86,015)	(67,063)
Equity in earnings/(loss) of affiliates, net of tax									(1,092)	(8,902)	(8,829)
Net Income/(Loss) from Continuing Operations									(233,170)	(181,117)	(163,728)
Capital Expenditures									18,550	18,942	22,435
Statement of Financial Position [Abstract]
Investments in affiliates, net	4,999				7,440				4,999	7,440
Long-Lived Assets	5,510,684				5,112,243				5,510,684	5,112,243
Total assets	5,575,846				5,318,990				5,575,846	5,318,990
Corporate [Member] | Domestic [Member]
Income Statement [Abstract]
Operating revenue									0	0	0
Statement of Financial Position [Abstract]
Long-Lived Assets	4,764,740				4,366,304				4,764,740	4,366,304
Corporate [Member] | Foreign [Member]
Income Statement [Abstract]
Operating revenue									12	39	31
Statement of Financial Position [Abstract]
Long-Lived Assets	745,944				745,939				745,944	745,939
Eliminations [Member]
Income Statement [Abstract]
Operating revenue									(10,099)	(10,330)	(9,821)
Depreciation and amortization									0	0	0
Operating Income/(Loss)									0	0	0
Equity in earnings/(loss) of affiliates, net of tax									0	0	0
Net Income/(Loss) from Continuing Operations									0	0	(11,965)
Capital Expenditures									0	0	0
Statement of Financial Position [Abstract]
Investments in affiliates, net	0				0				0	0
Long-Lived Assets	(5,425,500)				(5,020,521)				(5,425,500)	(5,020,521)
Total assets	(5,426,149)				(5,021,152)				(5,426,149)	(5,021,152)
Eliminations [Member] | Domestic [Member]
Income Statement [Abstract]
Operating revenue									(10,099)	(10,330)	(9,821)
Statement of Financial Position [Abstract]
Long-Lived Assets	(4,679,560)				(4,274,582)				(4,679,560)	(4,274,582)
Eliminations [Member] | Foreign [Member]
Income Statement [Abstract]
Operating revenue									0	0	$ 0
Statement of Financial Position [Abstract]
Long-Lived Assets	$ (745,940)				$ (745,939)				$ (745,940)	$ (745,939)