Liberty Broadband Corporation Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Principles (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 232,387	$ 227,044	$ 217,566	$ 217,736	$ 234,922	$ 210,146	$ 233,490	$ 61,204	$ 894,733	$ 739,762	$ 23,817
Lease, grant, and revenue from subsidies
Disaggregation of Revenue [Line Items]
Revenue									88,946	79,672
GCI Holdings \| Consumer Revenue \| Wireless
Disaggregation of Revenue [Line Items]
Revenue									118,425	94,713
GCI Holdings \| Consumer Revenue \| Data
Disaggregation of Revenue [Line Items]
Revenue									169,332	130,631
GCI Holdings \| Consumer Revenue \| Video
Disaggregation of Revenue [Line Items]
Revenue									83,928	72,826
GCI Holdings \| Consumer Revenue \| Voice
Disaggregation of Revenue [Line Items]
Revenue									16,479	14,792
GCI Holdings \| Business Revenue \| Wireless
Disaggregation of Revenue [Line Items]
Revenue									76,795	63,481
GCI Holdings \| Business Revenue \| Data
Disaggregation of Revenue [Line Items]
Revenue									273,847	223,121
GCI Holdings \| Business Revenue \| Video
Disaggregation of Revenue [Line Items]
Revenue									16,170	16,786
GCI Holdings \| Business Revenue \| Voice
Disaggregation of Revenue [Line Items]
Revenue									25,740	19,820
Evite
Disaggregation of Revenue [Line Items]
Revenue									$ 25,071	$ 23,920