Share-Based Compensation and Capital Stock Summary Of Activity Related To Restricted Stock Grants (Details) (Restricted Stock [Member], USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Share-Based Compensation and Capital Stock [Line Items]
Granted - shares	85,792	129,793
Weighted average grant date fair value per share (in dollars per share)	$ 63.46	$ 46.71
Aggregate grant date fair value	$ 5,445	$ 6,062
Restricted shares forfeited	4,778	1,332
Vesting service period of shares granted		4 years
Fair value of shares vested	$ 10,684	$ 7,269
Minimum [Member]
Share-Based Compensation and Capital Stock [Line Items]
Vesting service period of shares granted	3 years
Maximum [Member]
Share-Based Compensation and Capital Stock [Line Items]
Vesting service period of shares granted	4 years