Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

The following table summarizes compensation expense (a component of general and administrative expenses and property operating expenses) recognized for the periods presented (in thousands):

	Year Ended December 31,
	2018		2017		2016
Stock options	$	—	$	10	$	266
Restricted stock	27,646		19,092		28,603
	$	27,646	$	19,102	$	28,869

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

The following table summarizes information about non-vested restricted stock incentive awards as of and for the year ended December 31, 2018: 

	Restricted Stock
	Number of Shares (000's)		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2017	698		$	61.00
Vested	(166	)	63.88
Granted	723		54.16
Terminated	(35	)	60.90
Non-vested at December 31, 2018	1,220		$	62.56