Share-Based Compensation (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended					12 Months Ended														12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 2009 Stock Incentive Plan [Member]	Feb. 13, 2013 Common Stock Authorized, Subject to Stockholder Approval at May 8, 2013 Annual Meeting [Member]	Dec. 31, 2012 1997 Employee Stock Purchase Plan [Member]	Dec. 31, 2012 Stock Options Granted To Non Employee Directors [Member]	Dec. 31, 2012 Restricted Stock Units Granted To Employees With Ratable Vesting [Member]	Dec. 31, 2012 Restricted Stock Units Granted To Employees With Cliff Vesting [Member]	Dec. 31, 2012 Restricted Stock Units Granted To Non Employee Directors [Member]	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2010 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2012 Deferred Stock Units With Vesting Conditions [Member]	Dec. 31, 2012 Deferred Stock Units [Member]	Dec. 31, 2011 Deferred Stock Units [Member]	Dec. 31, 2010 Deferred Stock Units [Member]	Dec. 31, 2012 Stock Options And Stock Appreciation Rights [Member]	Dec. 31, 2012 Awards Other Than Stock Options And Stock Appreciation Rights [Member]	Dec. 31, 2012 Stock Options Granted To Employees With Ratable Vesting [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2012 Options Granted After January 1, 2006 [Member]	Dec. 31, 2012 Options Granted Prior To January 1, 2006 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant under share-based incentive plans				5,200,000	10,200,000	1,590,000
Ratio of shares issued under share-based awards to shares authorized under stock plans																		1 to 1	2 to 1
Shares available for grant under share-based incentive plans				2,537,440		151,064
Common stock issued in connection with the Employee Stock Purchase Plan	51,000	58,000	64,000
Discount from market value for employee stock purchase rights						15.00%
Unrecognized compensation expense, net of estimated forfeitures, for unvested share-based compensation awards outstanding	$ 33.3
Weighted average recognition period for unrecognized compensation expense, in years	1 year 7 months 9 days
Vesting period							1 year	5 years	3 years	1 year				1 year						5 years
Intrinsic value of stock options exercised	45.8	54.7	60.1
Number of unissued shares of common stock each DSU represents right to receive															1
Percentage of unvested share-based awards to vest upon change in control											25%										25%
Fair value of awards vested during period											13.3	12.4	7.9		0.4	0.4	0.5
Fair value of options vested during period	$ 8.3	$ 6.6	$ 8.4
Stock Options Maximum Contractual Term																						7 years	10 years