Commitments and Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Operating ground leases [Abstract]
Rental property expense	$ 3,400	$ 3,400	$ 2,800
Operating ground leases, scheduled future minimum payments [Abstract]
Operating leases, future minimum payments, 2016	3,033
Operating leases, future minimum payments, 2017	3,067
Operating leases, future minimum payments, 2018	3,103
Operating leases, future minimum payments, 2019	3,140
Operating leases, future minimum payments, 2020	3,179
Operating leases, future minimum payments, thereafter	109,157
Operating leases, total future minimum payments due	124,679
Lease and Contractual Commitments [Abstract]
Lease and contractual commitments	340,000
Accrued amount of lease and contractual commitments	55,900
Contingent Consideration [Abstract]
Asset acquisition, contingent consideration liability	$ 900	3,300	$ 0
Other Commitments [Abstract]
Rentable square feet of commercial real estate (in square feet) | ft²	32,486,000
Rentable square feet of commercial real estate under development (in square feet) | ft²	1,454,200
Asset Acquisition Contingent Consideration [Member]
Contingent Consideration [Abstract]
Acquisition purchase price	$ 5,200	15,800
Asset acquisition, contingent consideration liability	$ 900	$ 3,300
Contingent consideration expiration date	Jun. 30, 2019	Mar. 31, 2020
Accrued Severance Costs [Member]
Other Commitments [Abstract]
Expected severance costs to be incurred	$ 1,600
Total Severance Costs [Member]
Other Commitments [Abstract]
Expected severance costs to be incurred	$ 2,600
Office Property [Member]
Other Commitments [Abstract]
Rentable square feet of commercial real estate (in square feet) | ft²	468,000
Office Property [Member] | Closure of Division Office [Member]
Other Commitments [Abstract]
Rentable square feet of commercial real estate (in square feet) | ft²	468,000
Retail Property [Member]
Other Commitments [Abstract]
Rentable square feet of commercial real estate (in square feet) | ft²	776,000
Rentable square feet of commercial real estate under development (in square feet) | ft²	28,000
Retail Property [Member] | Closure of Division Office [Member]
Other Commitments [Abstract]
Rentable square feet of commercial real estate (in square feet) | ft²	776,000
Rentable square feet of commercial real estate under development (in square feet) | ft²	28,000