Equity Compensation Equity Compensation Deferred Directors (Details) - Director [Member] - Director Deferred Share Units [Member]	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Director deferred share units [Roll Forward]
Director deferred share units, beginning balance (in shares) | shares	110,741
Director deferred share units, issued (in shares) | shares	24,576
Director deferred share units, converted (in shares) | shares	(19,902)
Director deferred share units, ending balance (in shares) | shares	115,415
Weighted-average grant date fair value, director deferred share units, beginning balance (in dollars per share) | $ / shares	$ 21.98	[1]
Weighted-average grant date fair value, director deferred share units, issued (in dollars per share) | $ / shares	26.15	[1]
Weighted average grant date fair value director deferred share units, converted | $ / shares	21.50	[1]
Weighted-average grant date fair value, director deferred share units, ending balance (in dollars per share) | $ / shares	$ 22.95	[1]

[1] weighted-average