Leases - Third Party Leases, Cost and Accumulated Depreciation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Leases
Lease payments to related parties	$ 0	$ 0	$ 300,000
Office space leased in headquarters office and to third party lessees
Cost related to leased properties	304,300,000	304,300,000
Accumulated depreciation related to leased properties	$ 158,200,000	150,000,000.0
Terms of such leases
Lessor, renewal options included	true
Lessor, Operating Lease, Renewal Term	9 years
Operating lease income related to lease payments
Operating lease income related to lease payments	$ 6,400,000	6,300,000	5,900,000
Rental income paid by the related parties	0	400,000	400,000
Lease income related to variable lease payments	6,100,000	5,600,000	5,300,000
Future minimum rental income from related parties, amount	$ 0	$ 0	$ 0