Employee Benefits (Details 2) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Health Care and Life Insurance [Abstract]
Health care benefit expenses	$ 204	$ 241	$ 217

Represents the health care benefit expenses for the active employees health care plan.

No definition available.

Name:	ctq_HealthCareBenefitExpensesActiveEmployees
Namespace Prefix:	ctq_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration