Common Stock (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Treasury shares issued (in shares)	1,032,493
Common stock repurchases, value	$ 68,608	$ 19,037	$ 34,066
Treasury Stock [Member]
Common stock repurchases (in shares)	2,350,697	700,000	1,509,156
Common stock repurchases, value	$ 68,608	$ 19,037	$ 34,066
Common Stock [Member]
Employee stock plans (in shares)	1,104,099	608,227	2,075,385