Stock-Based Compensation (Restricted shares, performance-based restricted share units and performance share unit activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Number of Awards
Balance as of January 1, 2019 (in shares)	2,204,148
Awards granted (in shares)	1,051,053
Awards vested (in shares)	(801,504)
Awards forfeited, canceled or expired (in shares)	(379,425)
Performance-based adjustment (in shares)	40,914
Balance as of December 31, 2019 (in shares)	2,115,186	2,204,148
Weighted Average Grant Date Fair Value
Balance as of January 1, 2019 (in dollars per share)	$ 43.98
Awards granted (in dollars per share)	43.86	$ 51.64	$ 44.20
Awards vested (in dollars per share)	36.81
Awards forfeited, canceled or expired (in dollars per share)	45.98
Performance-based adjustment (in dollars per share)	44.86
Balance as of December 31, 2019 (in dollars per share)	$ 46.25	$ 43.98