Stock-Based Compensation (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Weighted-Average Grant Date Fair Value
Cash received from stock option exercises and employee stock purchases	$ 5.5
Cash used for shares withheld to satisfy employee tax obligations for NQOs exercised and RSUs converted	8.0
Shares authorized for future grant under stock plan (in shares)	1,200,000
RSUs
Summary of the Company's RSU activity
Outstanding at the beginning of the period	900,000	1,000,000	900,000
Granted	300,000	300,000	400,000
Issued	(400,000)	(400,000)	(300,000)
Outstanding at the end of the period	800,000	900,000	1,000,000
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period	$ 14.49	$ 11.76	$ 12.21
Granted	$ 25.26	$ 20.63	$ 11.41
Issued	$ 12.10	$ 12.51	$ 12.91
Outstanding at the end of the period	$ 18.90	$ 14.49	$ 11.76
Unrecognized compensation cost	4.9
RSUs | Minimum
Weighted-Average Grant Date Fair Value
Period over which unrecognized compensation costs will be recognized (in years)	1
RSUs | Maximum
Weighted-Average Grant Date Fair Value
Period over which unrecognized compensation costs will be recognized (in years)	3
PRSUs
Summary of the Company's RSU activity
Outstanding at the beginning of the period	700,000	600,000	500,000
Granted	100,000	100,000	300,000
Earned	200,000
Issued	(500,000)		(100,000)
Forfeited			(100,000)
Outstanding at the end of the period	500,000	700,000	600,000
Weighted-Average Grant Date Fair Value
Outstanding at the beginning of the period	$ 11.53	$ 9.77	$ 11.18
Granted	$ 25.03	$ 19.02	$ 10.95
Earned	$ 8.00
Issued	$ 8.28		$ 17.03
Forfeited			$ 7.37
Outstanding at the end of the period	$ 16.93	$ 11.53	$ 9.77
Unrecognized compensation cost	$ 3.9
Performance period (in years)	3 years	3 years	3 years
PRSUs | Minimum
Weighted-Average Grant Date Fair Value
Period over which unrecognized compensation costs will be recognized (in years)	1
Performance period (in years)	3 years
Current projections and performance targets estimated additional performance shares issuable	400,000
PRSUs | Maximum
Weighted-Average Grant Date Fair Value
Period over which unrecognized compensation costs will be recognized (in years)	3
Employee stock purchase plan
Weighted-Average Grant Date Fair Value
Maximum contribution by eligible employees as percentage of base earnings (as a percent)	10.00%
Common stock purchase price as percentage of fair market value (as a percent)	85.00%
Shares purchased under employee stock purchase plan (in shares)	31,448	30,585