Revenues - Revenues Disaggregated by Revenue Stream (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	$ 62,056	$ 69,388	$ 129,447	$ 139,006
Total revenues	268,180	266,820	540,766	532,982
Fiber Infrastructure
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	61,056	69,420	127,280	138,355
Total revenues	72,123	79,140	149,773	156,547
Fiber Infrastructure | Lit Backhaul
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	22,979	27,216	48,023	55,408
Fiber Infrastructure | Enterprise and Wholesale
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	21,327	19,628	42,327	38,886
Fiber Infrastructure | E-Rate and Government
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	15,926	21,821	35,290	42,758
Fiber Infrastructure | Other
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	824	755	1,640	1,303
Consumer CLEC
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers		(32)		651
Total revenues		(32)		651
Leasing
Disaggregation Of Revenue [Line Items]
Total revenue from contracts with customers	1,000		2,167
Total revenues	196,057	185,320	390,993	369,672
ASU 2016-02
Disaggregation Of Revenue [Line Items]
Total revenues	$ 206,124	$ 197,432	$ 411,319	$ 393,976