Debt Obligations and Credit Facilities - Unsecured Letters of Credit (Details) - USD ($)		5 Months Ended
	Nov. 06, 2019	Dec. 31, 2019	Dec. 09, 2019	Dec. 06, 2019	Dec. 05, 2019	Feb. 12, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Cash and investments		$ 639,300,000
Maiden Facility Agreement
Debt Instrument [Line Items]
Proceeds from credit facility agreement		445,000,000.0
Loan facilities | FAL Facility
Debt Instrument [Line Items]
Facility increase option						$ 400,000,000.0
Letters of Credit | Loan facilities | FAL Facility
Debt Instrument [Line Items]
Maximum borrowing capacity						375,000,000.0
Increase in borrowing capacity, limit						$ 25,000,000.0
Term extension	1 year
Letters of Credit | Loan facilities | 2018 Facility Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 120,000,000.0	$ 170,000,000.0
Increase in borrowing capacity, limit				$ 60,000,000.0
Letters of credit		115,300,000					$ 78,400,000
Letters of Credit | Loan facilities | Maiden Facility Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity		760,000,000.0
Increase in borrowing capacity, limit			$ 40,000,000.0
Letters of credit		$ 608,000,000.0