CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Supplemental disclosures of non-cash investing and financing activities
Common stock issued through the dividend reinvestment plan (in shares)					1,092	1,135
Common stock issued through the dividend reinvestment plan					$ 208,000	$ 190,000
Number of shares withheld to satisfy employees' tax withholding and other liabilities (in shares)					75,195	67,854
Shares withheld to satisfy employees' tax withholding and other liabilities, value					$ 14,206,000	$ 10,524,000
Stock issued during period, shares, share-based compensation, forfeited (in shares)					1,438
Stock issued during period, value, share-based compensation, forfeited					$ 250,000	648,000
Dividends declared but not paid	$ 213,403,000				213,403,000			$ 204,191,000
Change in redemption value of redeemable noncontrolling interest	45,000	$ 224,000	$ 291,000	$ 63,000
Increase (Decrease) in Derivative Liabilities					(4,198,000)
Increase (Decrease) in Derivative Assets					18,000
Cash flow hedge losses reclassified to earnings	(1,611,000)	(1,468,000)	(1,455,000)	(1,756,000)	(3,079,000)	$ (3,213,000)
Operating Lease, Right-of-Use Asset	100,377,000				100,377,000
Total lease liabilities	117,938,000				$ 117,938,000
Restricted Stock and Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares)					150,359	186,382
Restricted Stock Converted From Performance Shares
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares)					73,072	88,297
Restricted stock
Supplemental disclosures of non-cash investing and financing activities
Equity instruments granted (in shares)					77,287	98,085
Fair value of shares issued					$ 15,145,000	$ 15,837,000
Stock issued during period, shares, share-based compensation, forfeited (in shares)					1,438	4,434
Common stock
Supplemental disclosures of non-cash investing and financing activities
Dividends declared but not paid	212,822,000		203,472,000		$ 212,822,000	$ 203,472,000
Accumulated earnings less dividends
Supplemental disclosures of non-cash investing and financing activities
Change in redemption value of redeemable noncontrolling interest	$ 45,000	$ 224,000	$ 291,000	$ 63,000	$ 269,000	$ (354,000)
Accounting Standards Update 2016-02
Supplemental disclosures of non-cash investing and financing activities
Operating Lease, Right-of-Use Asset							$ 122,276,000
Total lease liabilities							$ 122,276,000