Employee Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2013

Employee Benefit and Other Plans [Abstract]

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

	For the three months ended March 31,
	2013		2012
	(in millions)
Share-based compensation expense	$	1.8	$	2.0

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	67,000		$	15.58
Exercised	(96,159	)	$	9.98
Canceled, Forfeited	(44,550	)	$	12.94
Options outstanding at March 31, 2013	5,445,636		$	11.85
Options exercisable at March 31, 2013	2,780,461		$	12.68
Expected to vest after March 31, 2013	2,019,114		$	10.99

Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Information

	For the three months ended March 31,
	2013		2012
Weighted-average grant date fair value	$	7.82	$	5.67

Schedule of Nonvested Share Activity

	Number of Shares		Weighted Average Grant Date Fair Value
Unvested shares at January 1, 2013	220,537		$	11.33
Granted	128,092		$	14.34
Vested	(31,431	)	$	13.56
Canceled, Forfeited	—		$	—
Unvested shares at March 31, 2013	317,198		$	12.33