Debt Obligations - Information on Borrowings under Current and Prior Credit Facility and Applicable Interest Rates (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Maximum amount outstanding under the credit facility during the period	$ 2,051,714	$ 1,300,401	$ 917,895
Average daily amount outstanding under the credit facility	$ 1,553,499	$ 914,012	$ 613,130
Weighted-average interest rate	3.80%	3.60%	2.70%