Commitments and contingencies (Notes)

12 Months Ended

Dec. 31, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and contingencies

Commitments and contingencies

Employee retirement savings plan

We have a retirement savings plan pursuant to Section 401(k) of the Internal Revenue Code (the “Code) whereby our employees may contribute a portion of their compensation to their respective retirement accounts in an amount not to exceed the maximum allowed under the Code. In addition to employee contributions, we have elected to provide company discretionary profit-sharing contributions (subject to statutory limitations), which amounted to approximately $4.9 million, $4.1 million, and $3.2 million for the years ended December 31, 2019, 2018, and 2017, respectively. Employees who participate in the plan are immediately vested in their contributions and in the contributions made on their behalf by the Company.

Concentration of credit risk

We maintain our cash and cash equivalents at insured financial institutions. The combined account balances at each institution periodically exceed the Federal Deposit Insurance Corporation (FDIC) insurance coverage of $250,000, and, as a result, there is a concentration of credit risk related to amounts in excess of FDIC insurance coverage. We have not experienced any losses to date on our invested cash.

We are dependent on rental revenue from relatively few tenants. The inability of any single tenant to make its lease payments could adversely affect our operations. As of December 31, 2019, we had 820 leases with a total of 622 tenants, and 135, or 46%, of our 291 properties were each leased to a single tenant. As of December 31, 2019, our three largest tenants, accounted for 4.1%, 3.1%, and 3.0% of our aggregate annual rental revenue individually, or 10.2% in the aggregate.

Commitments

As of December 31, 2019, remaining aggregate costs under contract for the construction of properties undergoing development, redevelopment, and improvements under the terms of leases approximated $1.1 billion. We expect payments for these obligations to occur over one year to three years, subject to capital planning adjustments from time to time. We may have the ability to cease the construction of certain properties, which would result in the reduction of our commitments. In addition, we have letters of credit and performance obligations aggregating $11.1 million primarily related to construction projects.

We are committed to funding approximately $229.5 million for non-real estate investments primarily related to our investments in limited partnerships. Our funding commitments expire at various dates over the next 12 years, with a weighted-average remaining period of 8.6 years as of December 31, 2019.