Employee Benefit Plans (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Awards, Cumulative Shares Issued	6,200,000		6,200,000
Share-based awards available for grant	3,400,000		3,400,000
Share-based compensation expense	$ 3,500,000	$ 3,200,000	$ 5,300,000	$ 5,300,000
Proceeds from Stock Options Exercised			2,288,000	631,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized compensation costs	14,800,000		14,800,000
Unamortized compensation costs, period for recognition			2 years
Weighted-average grant date fair value			$ 9.94	$ 4.96
Options Outstanding [Roll Forward]
Options outstanding at January 1, 2013			5,519,345
Options outstanding at January 1, 2013, weighted average exercise price, beginning balance			$ 11.78
Options granted, shares			474,259
Options granted, weighted average exercise price			$ 20.10
Options exercised, shares			(237,709)
Options exercised, weighted average exercise price			$ 9.49
Options cancelled or forfeited, shares			(166,300)
Options cancelled or forfeited, weighted average exercise price			$ 13.28
Options outstanding at June 30, 2013	5,589,595		5,589,595
Options outstanding, weighted average exercise price, ending balance	$ 12.54		$ 12.54
Options exercisable at June 30, 2013, shares	3,043,761		3,043,761
Options exercisable at June 30, 2012, weighted average exercise price	$ 12.66		$ 12.66
Expected to vest after June 30, 2013	1,903,333		1,903,333
Expected to Vest, Weighted Average Exercise Price	$ 12.52		$ 12.52
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized compensation costs	$ 6,300,000		$ 6,300,000
Unamortized compensation costs, period for recognition			2 years
Unvested Shares [Roll Forward]
Unvested shares at January 1, 2013			220,537
Unvested shares at January 1, 2013, Weighted-average grant date fair value			$ 11.33
Unvested shares granted			487,914
Unvested shares ganted, Weighted-average grant date fair value			$ 13.91
Unvested shares vested			(110,511)
Unvested shares vested, Weighted-average grant date fair value			$ 15.72
Unvested shares cancelled/forfeited			(30,832)
Unvested shares cancelled/forfeited, Weighted-average grant date fair value			$ 9.63
Unvested shares at June 30, 2013	567,108		567,108
Unvested shares at June 30, 2013, Weighted-average grant date fair value	$ 12.79		$ 12.79
Performance Stock Units
Unvested Shares [Roll Forward]
Unvested shares at January 1, 2013			0
Unvested shares at January 1, 2013, Weighted-average grant date fair value			$ 0
Unvested shares granted			122,776
Unvested shares ganted, Weighted-average grant date fair value			$ 25.14
Unvested shares at June 30, 2013	122,776		122,776
Unvested shares at June 30, 2013, Weighted-average grant date fair value	$ 25.14		$ 25.14