Stock-Based Compensation (Performance Vested Awards Return on Investment Targets) (Details) (Restricted Stock, USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Performance Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Incremental compensation cost	4,397
Return On Investment Target One [Member] | Performance Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Return On Investment Target Percentage	175.00%
Vesting Percentage	20.00%
Return On Investment Target Two [Member] | Performance Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Return On Investment Target Percentage	200.00%
Vesting Percentage	20.00%
Return On Investment Target Three [Member] | Performance Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Return On Investment Target Percentage	250.00%
Vesting Percentage	20.00%
Return On Investment Target Four [Member] | Performance Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Return On Investment Target Percentage	300.00%
Vesting Percentage	20.00%
Return On Investment Target Five [Member] | Performance Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Return On Investment Target Percentage	350.00%	400.00%
Vesting Percentage	20.00%
Maximum | Time Vested
Stock-Based Compensation [Line Items]
Award vesting period	5 years
Maximum | Time Vested | 2010 Equity Incentive Plan
Stock-Based Compensation [Line Items]
Award vesting period	5 years