Stock-Based Compensation (Narrative) (Details) $ / shares in Units, $ in Millions			1 Months Ended	12 Months Ended
	Sep. 15, 2020 USD ($) $ / shares shares	Jan. 01, 2019 shares	Jan. 31, 2019	Dec. 31, 2020 USD ($) item $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Apr. 27, 2015 shares
Stock-Based Compensation [Line Items]
Number of shares of common stock available for issuance				16,396,667
Number of shares of entity's common stock based on the fair market value of which maximum per-share exercise price is determined | $ / shares				$ 1
Period for which vested options will remain exercisable following termination of employment without cause				3 months
Period for which vested options will remain exercisable following termination of employment without cause in case of death, disability or retirement at normal retirement age				1 year
Number of shares of available for issuance				5,133,314
Stock-based compensation expense | $				$ 16	$ 14	$ 13
Stock-based compensation expense, net of tax | $				12	$ 10	$ 9
Total unrecognized compensation costs related to non-vested stock options and restricted share units | $				$ 33
Weighted-average period of recognition of stock-based compensation cost				1 year 9 months
Executives, Officers And Employees [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)				1,003,180	634,743	502,004
MSIP And Omnibus Incentive Plan [Member]
Stock-Based Compensation [Line Items]
Number of shares of Common Stock offered				0	0	0
Employee Stock Purchase Plan [Member]
Stock-Based Compensation [Line Items]
Discount established by the Company, maximum percent of the then-current fair market value				10.00%
Employee stock purchase plan, number of shares sold				45,840	14,429	0
Number of shares of common stock available for issuance				783,315			1,000,000
Stock Options [Member]
Stock-Based Compensation [Line Items]
Number of equal annual vesting installments | item				4
Granted to employees (in dollars per share) | $ / shares				$ 36.51	$ 40.04	$ 55.18
Weighted-average grant-date fair value (in dollars per share) | $ / shares				$ 11.23	$ 11.91	$ 17.68
Forfeiture rate (as a percent)				25.52%
Total intrinsic value of stock options exercised | $				$ 2	$ 10	$ 6
Total fair value of stock options vested | $				$ 5	$ 3	3
Vesting period				3 years	4 years
Stock Options [Member] | MSIP And Omnibus Incentive Plan [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)				1,003,180
Granted to employees (in dollars per share) | $ / shares				$ 36.52
Vesting period			10 years	8 years
Requisite service period				3 years
Super Performance Options Granted To CEO [Member] | Chief Executive Officer [Member]
Stock-Based Compensation [Line Items]
Forfeiture rate (as a percent)				0.00%
RSUs [Member]
Stock-Based Compensation [Line Items]
Number of equal annual vesting installments | item				3
Granted fair value | $	$ 2
Weighted average exercise price | $ / shares	$ 40.67
Granted to employees (in shares)				567,844
Granted to employees (in dollars per share) | $ / shares				$ 37.81
Total fair value of RSUs vested | $				$ 10	$ 8	$ 18
Number of shares of common stock into which each award will be converted upon vesting				1
RSUs [Member] | Executives, Officers And Employees [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)				567,844	516,775	354,931
Granted to employees (in dollars per share) | $ / shares				$ 37.81	$ 42.11	$ 52.40
RSUs [Member] | Executives From Strategic Acquisition [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)		136,092
RSUs [Member] | President, Terminix Commercial [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)	24,589
Retention award amount | $	$ 1
RSUs [Member] | President, Terminix Commercial [Member] | March 15, 2021 [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)	12,194
Performance Based Shares [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)				95,916	107,149
Granted to employees (in dollars per share) | $ / shares				$ 36.99	$ 40.04
Vesting period				3 years
Performance Based Shares [Member] | Nomor Executives [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)					87,920
Granted to employees (in dollars per share) | $ / shares					$ 56.87
Vesting period				3 years
Performance Based Shares [Member] | Executives From Strategic Acquisition [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)				38,178	8,912
Granted to employees (in dollars per share) | $ / shares				$ 36.35	$ 56.11
Vesting period				4 years
Spin-off [Member]
Stock-Based Compensation [Line Items]
Stock-based compensation expense | $					$ 3
Spin-off [Member] | Performance Based Shares [Member]
Stock-Based Compensation [Line Items]
Granted to employees (in shares)						0