Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Summary of Significant Accounting Policies (Details) $ in Millions		3 Months Ended		12 Months Ended
	Aug. 27, 2015 USD ($)	Dec. 31, 2015 USD ($) state	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) state
Operating revenues by products and services
Incremental increase in other operating revenues		$ 57	$ 158
CAF Phase 2 Support [Member]
Operating revenues by products and services
Federal support, total amount per agreement	$ 500
Contract or agreement term	6
Number of rural households and businesses	1,200,000
Number of states in which service is provided (states) | state		33		33
Incremental increase in other operating revenues				$ 215