Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended					12 Months Ended		12 Months Ended				12 Months Ended			12 Months Ended				1 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended									12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Plan 2009 [Member]	Feb. 28, 2009 Plan 2009 [Member]	Dec. 31, 2013 Plan 2007 [Member]	Dec. 31, 2007 Plan 2007 [Member]	Dec. 31, 2013 Plan 2004 [Member]	Dec. 31, 2012 Plan 2004 [Member]	Dec. 31, 2011 Plan 2004 [Member]	Apr. 30, 2004 Plan 2004 [Member]	Dec. 31, 2013 Plan 2004 Initial Options [Member] installment	Dec. 31, 2013 Plan 2001 [Member]	May 31, 2001 Plan 2001 [Member]	Dec. 31, 2013 ESPP 2010 [Member]	Dec. 31, 2012 ESPP 2010 [Member]	Jun. 30, 2011 ESPP 2010 [Member]	Jun. 30, 2010 ESPP 2010 [Member]	May 31, 2000 ESPP 2000 [Member]	Dec. 31, 2013 ESPP 2000 [Member]	Apr. 30, 1998 Plan 1998 [Member]	Dec. 31, 2013 Plan 1998 [Member]	Dec. 31, 2013 Director Plan 2000 [Member]	Dec. 31, 2013 Restricted Stock and ESPP [Member]	Dec. 31, 2012 Restricted Stock and ESPP [Member]	Dec. 31, 2011 Restricted Stock and ESPP [Member]	Dec. 31, 2013 Stock Options [Member]	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2013 Stock Options [Member] Plan 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option term				10 years		10 years		10 years													10 years						10 years
Options granted																											2,263,649	1,619,702	2,108,510		1,215,396
Options outstanding													13,500									55,990	0				7,616,404	9,112,032	9,136,677	8,025,411	1,178,979
Number of shares authorized					1,500,000		1,700,000	13,166,879			13,900,000			1,250,000				1,000,000	805,500		6,118,259
Common stock available for issuance								3,700,000
Number of shares in pool								1.7
Vesting rights percentage				25.00%		25.00%		25.00%
Vesting period				1 year		1 year		1 year
Periodic period for vesting term				3 years		3 years		3 years													4 years						4 years
Stock issued				75,255		42,500							1,101,241		121,845	144,903				805,437		5,064,910	177,086
Initial grants to each director								320,000
Grants on date of annual meeting								215,000
Grants to lead director								5,000
Number of vesting installments												36
Weighted average grant date fair aalue	$ 13.76	$ 8.95	$ 7.38
Intrinsic value, exercised in period	$ 43.5	$ 10.4	$ 3.0
Recorded stock-based compensation expense								6.1	4.7	2.9					1.0	0.7								23.0	15.0	11.0	15.9	9.6	7.5
Total unrecognized compensation costs related to non-vested share-based compensation.	27.6							5.6
Weighted average period over which costs will be recognized	1 year 4 months 17 days							1 year 2 months 4 days
Shares vested in period, fair value								$ 7.5	$ 4.0	$ 3.0
Percentage discount from offering date																			85.00%
Maximum employee subscription rate																	5.00%		5.00%
Available for future grant															544,207												3,432,083
Awarded								12,574,479
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number								6,250,180