Stock-based Compensation (Summary of Restricted Stock Awards Activity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted, number of shares	1,000	1,000	900
Shares granted, weighted-average grant-date fair value (in dollars per share)	$ 46.37	$ 38.82	$ 37.05
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding at the beginning of the year, number of shares	2,343
Shares outstanding at the beginning of the year, weighted-average grant-date fair value (in dollars per share)	$ 34.2
Shares granted, number of shares	958
Shares granted, weighted-average grant-date fair value (in dollars per share)	$ 46.4
Shares vested, number of shares	(978)
Shares vested, weighted-average grant-date fair value (in dollars per share)	$ 33.5
Shares forfeited, number of shares	(41)
Shares forfeited, weighted-average grant-date fair value (in dollars per share)	$ 46.8
Shares outstanding at the end of year, number of shares	2,282
Shares outstanding at the end of the year, weighted-average grant-date fair value (in dollars per share)	$ 39.4