Financing and Other Debt - Schedule of Debt (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,414,233,000	$ 2,461,048,000
Current portion of gross debt	245,608,000	404,233,000
Less: Unamortized debt issuance costs	(6,744,000)	(7,015,000)
Short-term debt, net	238,864,000	397,218,000
Long-term gross debt	2,168,625,000	2,056,815,000
Less: Unamortized debt issuance costs	(27,750,000)	(29,063,000)
Long-term debt, net	2,140,875,000	2,027,752,000
Lines of credit outstanding	1,700,000,000
Loan Participations and Assignments
Debt Instrument [Line Items]
Long-term debt, gross	140,965,000	184,990,000
Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity	666,282,000	405,965,000
Secured debt
Debt Instrument [Line Items]
Long-term debt, gross	111,556,000	126,901,000
Line of Credit \| Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Long-term debt, gross	0	136,535,000
Line of Credit \| Secured debt \| 2016 Credit Agreement
Debt Instrument [Line Items]
Long-term debt, gross	1,753,904,000	1,602,875,000
Notes payable \| Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	400,000,000	400,000,000
Letter of Credit \| Revolving line-of-credit facility under 2016 Credit Agreement \| 2016 Credit Agreement
Debt Instrument [Line Items]
Lines of credit outstanding	$ 53,718,000	$ 27,500,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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