Employee Incentive Plan (Share-Based Compensation Schedule) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Restricted Stock Units (RSUs) [Member]
Number of Shares
Non-vested beginning of period (Units)	1,003,159
Granted (Units)	580,785
Vested (Units)	(277,404)	[1]
Forfeited (Units)	(36,758)
Non-vested, end of period (Units)	1,269,782
Aggregate intrinsic value, end of period (in thousands)	$ 26,183
Weighted Average Grant-Date Fair Value
Non-vested beginning of period	$ 13.31
Granted	$ 15.83
Vested	$ 9.00	[1]
Forfeited	$ 12.43
Non-vested, end of period	$ 15.43
Vested units withheld for payroll taxes on behalf of employees	81,321
Restricted Stock [Member]
Number of Shares
Non-vested beginning of period (Units)	1,329,162
Granted (Units)	587,571
Vested (Units)	(281,145)
Forfeited (Units)	(43,692)
Non-vested, end of period (Units)	1,591,896
Aggregate intrinsic value, end of period (in thousands)	$ 31,456
Weighted Average Grant-Date Fair Value
Non-vested beginning of period	$ 9.75
Granted	$ 14.69
Vested	$ 7.77
Forfeited	$ 11.43
Non-vested, end of period	$ 11.87
Vested units withheld for payroll taxes on behalf of employees	79,723

[1] Vested units include 81,321 units withheld for payroll taxes paid on behalf of employees.