Weighted Average Shares Outstanding (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended						12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 05, 2011 3.75% Convertible Notes [Member] Convertible Debt [Member]	Dec. 31, 2013 3.375% Convertible Notes [Member] Convertible Debt [Member]	Dec. 31, 2012 3.375% Convertible Notes [Member] Convertible Debt [Member]	Dec. 31, 2013 Stock options [Member]	Dec. 31, 2012 Stock options [Member]	Dec. 31, 2011 Stock options [Member]	Dec. 31, 2013 Stock options [Member]	Dec. 31, 2012 Stock options [Member]	Dec. 31, 2011 Stock options [Member]	Dec. 31, 2013 Restricted stock units [Member]	Dec. 31, 2012 Restricted stock units [Member]	Dec. 31, 2011 Restricted stock units [Member]	Dec. 31, 2013 Non Employee Director Deferred Stock Plan [Member]	Dec. 31, 2012 Non Employee Director Deferred Stock Plan [Member]	Dec. 31, 2011 Non Employee Director Deferred Stock Plan [Member]
Weighted Average Shares Outstanding [Line Items]
Basic (in shares)	53,860,308	54,626,453	55,214,586
Dilutive effect of:
Shares attributable to share-based payment arrangements (in shares)										575,202	478,462	645,280	280,488	70,554	19,089	48,025	48,988	52,927
Diluted (in shares)	54,973,344	55,224,457	55,931,882
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount							133,162	336,892	787,809
Convertible notes				$ 92,500	$ 55,636	$ 55,636
Convertible notes stated interest rate				3.75%	3.375%
Debt Instrument, Convertible, Conversion Price					$ 28.31
Trading Days Used To Compute Average Closing Price of Stock for Dilutive Effect Comparison	30 days
Incremental Common Shares Attributable to Conversion of Debt Securities	209,321	0	0