Revenue Revenue (Policies)	6 Months Ended
Revenue Revenue (Policies)	Jun. 30, 2019
Revenue [Abstract]
Revenue Outright Sale Policy [Policy Text Block]	In transactions involving security systems that are sold outright to the customer, the Company’s performance obligations generally include monitoring, related services, and the sale and installation of the security systems. For such arrangements, the Company allocates a portion of the transaction price to each performance obligation based on a relative standalone selling price. Revenue associated with the sale and installation of security systems is recognized once installation is complete and is reflected in installation and other revenue in the Condensed Consolidated Statements of Operations. Revenue associated with monitoring and related services is recognized as those services are provided and is reflected in monitoring and related services revenue in the Condensed Consolidated Statements of Operations.
Revenue from Contract with Customer [Policy Text Block]	The Company generates revenue primarily through contractual monthly recurring fees received for monitoring and related services provided to customers. In transactions in which the Company provides monitoring and related services but retains ownership of the security systems, the Company’s performance obligations primarily include monitoring, related services (such as maintenance agreements), and a material right associated with the non-refundable fees received in connection with the initiation of a monitoring contract (referred to as deferred subscriber acquisition revenue) that the customer will not need to pay upon a renewal of the contract. The portion of the transaction price associated with monitoring and related services revenue is recognized when the services are provided to the customer and is reflected in monitoring and related services revenue in the Condensed Consolidated Statements of Operations.
Deferred Subscriber Acquisition Costs [Policy Text Block]	Deferred subscriber acquisition costs, net represent incremental selling expenses (primarily commissions) related to acquiring customers. Amortization expense relating to deferred subscriber acquisition costs included in selling, general and administrative expenses in the Condensed Consolidated Statements of Operations was $20 million and $14 million for the quarters ended June 30, 2019 and 2018, respectively, and $38 million and $27 million for the six months ended June 30, 2019 and 2018, respectively. Deferred subscriber acquisition revenue is deferred and recorded as deferred subscriber acquisition revenue in the Condensed Consolidated Balance Sheets upon initiation of a monitoring contract. Deferred subscriber acquisition revenue is amortized on a pooled basis into installation and other revenue in the Condensed Consolidated Statements of Operations over the estimated life of the customer relationship using an accelerated method consistent with the amortization of subscriber system assets and deferred subscriber acquisition costs associated with the transaction.
Revenue Recognition, Deferred Revenue [Policy Text Block]	Customer billings for services not yet rendered are deferred and recognized as revenue as services are provided. These fees are recorded as current deferred revenue in the Condensed Consolidated Balance Sheets as the Company expects to satisfy any remaining performance obligations, as well as recognize the related revenue, within the next twelve months. Accordingly, the Company has applied the practical expedient regarding deferred revenue to exclude the value of remaining performance obligations if (i) the contract has an original expected term of one year or less or (ii) the Company recognizes revenue in proportion to the amount it has the right to invoice for services performed.