Leases

We lease office space and equipment under non-cancelable operating leases. We recognize operating lease expense on a straight-line basis over the lease term. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Most leases include one or more options to renew, with renewal terms that can extend the lease term from one to seven years. The exercise of lease renewal options is at our sole discretion. Certain of our lease agreements include rental payments that are adjusted periodically for inflation. Our lease agreements do not contain any material residual value guarantees or material restrictive covenants.

The table below summarizes the carrying amount of our operating lease assets and liabilities:



Leases	Classification	As of March 31, 2019
Assets
Operating lease assets	Operating lease assets	$	146,389
Total lease assets		$	146,389
Liabilities
Current
Operating lease liabilities	Accounts payable, accrued expenses and other	$	28,925
Noncurrent
Operating lease liabilities	Noncurrent operating lease liabilities	173,874
Total lease liabilities		$	202,799

The table below summarizes total lease cost for the three months ended March 31, 2019:



	Three Months Ended March 31,
Lease Cost	2019
Operating lease costs	$	10,865
Short-term lease costs	863
Variable lease costs	3,013
Sublease income	(1,197		)
Total lease cost	$	13,544

We sublease certain of our leased office spaces to third parties. Our sublease portfolio consists of leases of office space that we have abandoned before the lease term expiration. Operating lease expense on abandoned office space is reduced by sublease rental income, which is recorded to SG&A expenses on the Condensed Consolidated Statements of Comprehensive Income. Our sublease arrangements do not contain renewal options or restrictive covenants. We estimate that future sublease rental income to be $3.7 million in 2019, $4.6 million in 2020, $4.2 million in 2021, $0.7 million in 2022, $0.6 million in 2023 and $0.9 million in years beyond 2023.

The maturity analysis below summarizes the remaining future undiscounted cash flows for our operating leases, a reconciliation to operating lease liabilities reported on the Condensed Consolidated Balance Sheet, our weighted-average remaining lease term and weighted average discount rate:



	As of March 31, 2019
	As of March 31, 2019
2019	$	29,415
2020	47,363
2021	45,395
2022	26,364
2023	22,038
Thereafter	83,068
Total future lease payments	253,643
Less: imputed interest	(50,844		)
Total	$	202,799

Weighted Average Remaining Lease Term (years)
Operating leases	6.5

Weighted Average Discount Rate
Operating leases	6.2		%

The table below summarizes cash paid for our operating lease liabilities and other non-cash information:



	Three Months Ended March 31,
	2019
Cash paid for amounts included in the measurement of operating lease liabilities	$	11,535

Operating lease assets obtained in exchange for lease liabilities	$	4,045

Operating Lease Commitments

Under Topic 840, our future minimum payments for all operating lease obligations that have initial non-cancelable lease terms exceeding one year, net of rental income from subleases as of December 31, 2018 were as follows:



	Operating Leases		Sublease Rental Income
	Operating Leases		Sublease Rental Income
2019	$	49,757	$	4,760
2020	47,084		3,944
2021	44,480		3,864
2022	24,471		707
2023	20,309		614
Thereafter	75,190		939
Total	$	261,291	$	14,828