Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		0 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Mar. 08, 2012 2011 Stock Repurchase Program [Member]	May 02, 2011 2011 Stock Repurchase Program [Member]	Jun. 30, 2013 2011 Stock Repurchase Program [Member]	Dec. 31, 2012 2011 Stock Repurchase Program [Member]
Significant Accounting Policies [Line Items]
Common stock equivalents (in shares)	718,000	782,000	849,000	1,278,000
Anti-dilutive securities excluded from computation of diluted earnings per share (in shares)	1,075,000	1,744,000	1,630,000	868,000
Stock repurchase program authorized amount					$ 323.7	$ 300.0
Stock repurchase program remaining authorized repurchase amount							$ 280.0	$ 350.0