401(k) Plan	12 Months Ended
Dec. 31, 2017
Postemployment Benefits [Abstract]
401(k) PLAN	401(k) PLAN Under our 401(k) plan, corporate participants may direct the investment of contributions to their accounts among certain investments. We match individual employee 401(k) plan contributions at the rate of $0.50 for every dollar contributed by employees subject to a cap. We recorded matching contributions to the 401(k) plan of $6 million, $5 million, and $5 million during the years ended December 31, 2017, 2016, and 2015, respectively, which are reflected in various operating expense lines within the accompanying consolidated statements of income and comprehensive income. We also maintain multiple employer defined contribution plans, which cover WSEs for client companies electing to participate in the plan and for their internal staff employees. We contribute, on behalf of each participating client, varying amounts based on the clients’ policies and serviced employee elections.

401(k) Plan

12 Months Ended

Dec. 31, 2017

Under our 401(k) plan, corporate participants may direct the investment of contributions to their accounts among certain investments. We match individual employee 401(k) plan contributions at the rate of $0.50 for every dollar contributed by employees subject to a cap. We recorded matching contributions to the 401(k) plan of $6 million, $5 million, and $5 million during the years ended December 31, 2017, 2016, and 2015, respectively, which are reflected in various operating expense lines within the accompanying consolidated statements of income and comprehensive income.

We also maintain multiple employer defined contribution plans, which cover WSEs for client companies electing to participate in the plan and for their internal staff employees. We contribute, on behalf of each participating client, varying amounts based on the clients’ policies and serviced employee elections.