Share-Based Compensation and Capital Stock Summary Of Activity Related To PVRSU Grants (Details) (Performance Vested Restricted Stock Units [Member], USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Performance Vested Restricted Stock Units [Member]
Share-Based Compensation and Capital Stock [Line Items]
Performance vested restricted stock units granted at target	30,353	43,871
Weighted average grant date fair value per share (in dollars per share)	$ 63.47	$ 45.59
Aggregate grant date fair value	$ 1,927	$ 2,000
Stock units forfeited	0	0
Requisite service period	3 years	3 years