Share-Based Payments (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended			0 Months Ended		0 Months Ended	3 Months Ended		6 Months Ended				3 Months Ended		6 Months Ended		0 Months Ended	6 Months Ended	0 Months Ended	3 Months Ended		6 Months Ended		0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Members of the Board of Directors	Jun. 11, 2013 Incentive Award Plan, 2013	Jun. 30, 2013 Incentive Award Plan, 2013	Jun. 11, 2013 Incentive Award Plan, 2013 Minimum	Jun. 30, 2013 Employee stock options	Jun. 30, 2012 Employee stock options	Jun. 30, 2013 Employee stock options	Jun. 30, 2012 Employee stock options	Jun. 30, 2013 Annual Merit Awards	Jun. 30, 2013 New Hire Awards	Jun. 30, 2013 Stock options	Jun. 30, 2012 Stock options	Jun. 30, 2013 Stock options	Jun. 30, 2012 Stock options	Jun. 11, 2013 Stock options Incentive Award Plan, 2013	Jun. 30, 2013 Incentive stock options	Jun. 11, 2013 Incentive stock options Incentive Award Plan, 2013	Jun. 30, 2013 Restricted stock awards	Jun. 30, 2012 Restricted stock awards	Jun. 30, 2013 Restricted stock awards	Jun. 30, 2012 Restricted stock awards	Jun. 11, 2013 Restricted stock awards Incentive Award Plan, 2013
Share-Based Payments
Number of shares reserved for issuance						3,300,000
Number of shares reserved for each share subject to the option that was granted under the Prior Plans						$ 1
Maximum number of shares reserved for the shares subject to the options that were granted under the Prior Plans						5,386,094
Number of shares reserved for each share subject to an award other than a stock option that was granted under the Prior Plans						$ 1.35
Maximum number of shares reserved for the shares subject to other than the stock options that were granted under the Prior Plans						1,137,394
Shares available for grant							3,167,815
Threshold combined voting power of all classes of stock held by employees considered for grant (as a percent)						10.00%
Fair market value of common stock on the date of grant (as a percent)								110.00%
Award vesting period																					4 years					4 years
Award expiration period from the date of grant																			10 years
Allocated share-based compensation	$ 3.3	$ 3.5	$ 6.2	$ 6.7					$ 2.2	$ 2.0	$ 4.1	$ 3.8										$ 1.1	$ 1.5	$ 2.0	$ 2.9
Granted (in shares)					142,000								1,025,771	129,275						1,297,046
Weighted average grant date fair value of options granted (in dollars per share)															$ 7.83	$ 8.83	$ 7.29	$ 9.25