Capital Stock and Share Based Compensation Plans - Additional restricted stock and restricted stock unit vesting (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares and units vested	$ 12,906
Tax benefits realized on shares and units vested	4,840	[1]
Restricted Stock and Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares and units vested			16,565		23,326
Tax benefits realized on shares and units vested			$ 6,212	[1]	$ 8,747	[1]

[1] Benefits for 2013 to be recognized in future years when realizable.