Segment Information (Narrative) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information [Line Items]
Operating revenue	$ 467,642	$ 436,727	$ 385,086	$ 352,920	$ 352,841	$ 375,571	$ 374,738	$ 337,723	$ 1,642,375	$ 1,440,873	$ 1,436,370
Number of Reportable Segments | segment									2
Depreciation and amortization									$ 174,445	175,100	181,142
Operating Segments | PIRM
Segment Reporting Information [Line Items]
Operating revenue									681,912	663,016	646,804
Segment Reporting Information Intercompany Revenue									10,200	6,200	4,000
Segment Reporting Information Intercompany Expense									2,200	3,300	3,000
Depreciation and amortization									93,640	94,862	95,866
Operating Segments | UWS
Segment Reporting Information [Line Items]
Operating revenue									972,831	787,368	796,550
Segment Reporting Information Intercompany Revenue									2,200	3,300	3,000
Segment Reporting Information Intercompany Expense									3,400	4,300	4,000
Depreciation and amortization									$ 48,126	$ 51,337	$ 62,011