Leases (Policies)	12 Months Ended
Leases (Policies)	Dec. 31, 2016
Leases [Abstract]
Leases, Policy	We lease substantially all our office space under operating leases and equipment under operating and capital leases. Office leases may include renewal options. In circumstances where the exercise of a renewal option is reasonably assured at the inception of the lease, the renewal period is included in the determination of the lease term. Office leases may also include scheduled rent increases and concessions, such as rent abatements and landlord incentives and tenant improvement allowances. Scheduled rent increases are recognized on a straight-line basis over the lease term and concessions are recorded as deferred rent and are amortized in rent expense on a straight-line basis over the lease term. Certain office leases require payment of real estate taxes and other occupancy costs and these costs are not included in rent expense. Leasehold improvements made at inception or during the lease term are amortized over the shorter of the asset life or the lease term, which may include renewal periods where the renewal is reasonably assured.

Disclosure of accounting policy for leasing arrangements (both lessor and lessee). This disclosure may address (1) lease classification (that is, operating versus capital), (2) how the term of a lease is determined (for example, the circumstances in which a renewal option is considered part of the lease term), (3) how rental revenue or expense is recognized for a lease that contains rent escalations, (4) an entity's accounting treatment for deferred rent, including that which arises from lease incentives, rent abatements, rent holidays, or tenant allowances (5) an entity's accounting treatment for contingent rental payments and (6) an entity's policy for reviewing, at least annually, the residual values of sales-type and direct-finance leases. The disclosure also may indicate how the entity accounts for its capital leases, leveraged leases or sale-leaseback transactions.