Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, Number of Shares, Beginning Balance	653,516
Numbers of Shares, Granted	0
Number of Shares, Exercised	(419,158)
Numbers of Shares, Cancelled	(373)
Options outstanding, Number of Shares, Ending Balance	233,985	653,516
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted Average Exercise Price, Beginning of Period (in dollars per share)	$ 16.30
Weighted Average Exercise Price, Granted (in dollars per share)	$ 0.00
Weighted Average Exercise Price, Exercised (in dollars per share)	$ 16.04
Weighted Average Exercise Price, Cancelled (in dollars per share)	$ 14.47
Weighted Average Exercise Price, End of Period (in dollars per share)	$ 16.78	$ 16.30
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Terms (in years)	4 years 1 month 6 days
Options outstanding, Aggregate Intrinsic Value	$ 4.5
Number of Shares, Options exercisable	233,985	223,016
Weighted Average Exercise Price, Options exercisable (in dollars per share)	$ 16.78	$ 16.42
Weighted Average Remaining Contractual Terms, Options exercisable (in years)	4 years 1 month 6 days	2 years 1 month 6 days
Aggregate Instrinsic Value, Options exercisable	$ 4.5	$ 3.0