Employee Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2013

Employee Benefit and Other Plans [Abstract]

Schedule of Employee Benefit Plans

	For the three months ended June 30,				For the six months ended June 30,
	2013		2012		2013		2012
	(in millions)
Share-based compensation expense	$	3.5	$	3.2	$	5.3	$	5.3

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award

	Number of Stock Options		Weighted Average Exercise Price
Options outstanding at January 1, 2013	5,519,345		$	11.78
Granted	474,259		$	20.10
Exercised	(237,709	)	$	9.49
Canceled, Forfeited	(166,300	)	$	13.28
Options outstanding at June 30, 2013	5,589,595		$	12.54
Options exercisable at June 30, 2013	3,043,761		$	12.66
Expected to vest after June 30, 2013	1,903,333		$	12.52

Schedule of Stock Option Activity

	For the six months ended June 30,
	2013		2012
Weighted-average grant date fair value	$	9.94	$	4.96

Schedule of Restricted Stock Units Activity

	Number of Shares		Weighted Average Grant Date Fair Value
Unvested shares at January 1, 2013	220,537		$	11.33
Granted	487,914		$	13.91
Vested	(110,511	)	$	15.72
Canceled, Forfeited	(30,832	)	$	9.63
Unvested shares at June 30, 2013	567,108		$	12.79

Schedule of Performance Stock Units Activity

Performance Stock Units: The following table summarizes information related to our performance stock units:

	Number of Shares	Weighted Average Grant Date Fair Value
Unvested shares at January 1, 2013	—	$	—
Granted	122,776	$	25.14
Unvested shares at June 30, 2013	122,776	$	25.14