Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

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

Restricted shares, performance-based restricted share units and performance share unit activity

The following table presents activity for non-vested RSUs, performance-based RSUs and performance share units under the Plan in 2017.

	Number of Awards		Weighted-Average Grant Date Fair Value
Balance as of January 1, 2017	2,131,782		$	33.28
Awards granted	1,010,741		44.20
Awards vested	(930,616	)	33.31
Awards forfeited, canceled or expired	(290,296	)	36.20
Performance-based adjustment	149,126		44.07
Balance as of December 31, 2017	2,070,737		$	38.92