Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Risk-free interest rate assumption used in valuing an instrument.

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Fair value as of the balance sheet date of all interest rate derivative assets designated as cash flow hedging instruments.

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

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Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes receivable	$ 13,332		$ 13,332		$ 10,481
Notes payable	2,944,995		2,944,995		1,363,925
Unsecured credit facilities	563,031		563,031		278,495
Provision for impairment	0	$ 0	0	$ (1,666)
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	29,839		29,839		28,588
Available-for-sale Securities	7,009		7,009		7,420
Interest Rate Derivative Assets, at Fair Value	10,499		10,499		11,622
Total	47,347		47,347		47,630
Derivative instruments, at fair value	(1,664)		(1,664)		(580)
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	29,839		29,839		28,588
Available-for-sale Securities	0		0		0
Interest Rate Derivative Assets, at Fair Value	0		0		0
Total	29,839		29,839		28,588
Derivative instruments, at fair value	0		0		0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes Payable, Fair Value	2,988,426		2,988,426		1,435,000
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0		0		0
Available-for-sale Securities	7,009		7,009		7,420
Interest Rate Derivative Assets, at Fair Value	10,499		10,499		11,622
Total	17,508		17,508		19,042
Derivative instruments, at fair value	(1,664)		(1,664)		(580)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notes Receivable, Fair Value	13,223		13,223		10,380
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Securities	0		0		0
Available-for-sale Securities	0		0		0
Interest Rate Derivative Assets, at Fair Value	0		0		0
Total	0		0		0
Derivative instruments, at fair value	0		$ 0		$ 0
Unsecured Credit Facilities [Member] \| Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk Free Interest Rate			2.00%		1.50%
Unsecured Credit Facilities [Member] \| Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk Free Interest Rate			2.00%		1.60%
Unsecured Credit Facilities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured credit facilities, Fair Value	$ 565,000		$ 565,000		$ 279,700
Notes Payable, Other Payables [Member] \| Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk Free Interest Rate			3.10%		2.90%
Notes Payable, Other Payables [Member] \| Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk Free Interest Rate			4.10%		3.90%
Notes Receivable [Member] \| Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk Free Interest Rate			7.30%		7.20%
Notes Receivable [Member] \| Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Risk Free Interest Rate			7.30%		7.20%