Debt - Senior Unsecured Notes Exchangeable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 31, 2014
Debt Instrument [Line Items]
Interest expense	$ 89,907,000	$ 79,246,000	$ 79,623,000
Amortization expense of deferred financing costs	$ 4,100,000	3,800,000	4,100,000
Senior unsecured notes - exchangeable | Senior unsecured notes - exchangeable
Debt Instrument [Line Items]
Face amount				$ 250,000,000.0
Stated interest rate (as a percent)				2.625%
Interest on note		6,100,000	9,900,000
Interest expense		4,100,000	6,600,000
Accretion of debt discount		1,600,000	2,700,000
Amortization expense of deferred financing costs		$ 400,000	$ 600,000