Performance Share Status (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
2012 LTC Plan | Market-Based Performance Condition One
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 13.78
Estimated Number of Performance Shares to be Issued	172
Maximum Number of Performance Shares that could Potentially be Issued	244
2012 LTC Plan | Market-Based Performance Condition Two
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 16.65
Estimated Number of Performance Shares to be Issued	41
Maximum Number of Performance Shares that could Potentially be Issued	58
2012 LTC Plan | Non-Market-Based Performance Condition One
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 10.02
Estimated Number of Performance Shares to be Issued	0
Maximum Number of Performance Shares that could Potentially be Issued	244
2012 LTC Plan | Non-Market-Based Performance Condition Two
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 12.74
Estimated Number of Performance Shares to be Issued	0
Maximum Number of Performance Shares that could Potentially be Issued	58
2011 LTC Plan | Market-Based Performance Condition One
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 23.89
Estimated Number of Performance Shares to be Issued	39
Maximum Number of Performance Shares that could Potentially be Issued	131
2011 LTC Plan | Market-Based Performance Condition Two
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 10.61
Estimated Number of Performance Shares to be Issued	9
Maximum Number of Performance Shares that could Potentially be Issued	32
2011 LTC Plan | Non-Market-Based Performance Condition One
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 17.13
Estimated Number of Performance Shares to be Issued	0
Maximum Number of Performance Shares that could Potentially be Issued	131
2011 LTC Plan | Non-Market-Based Performance Condition Two
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 12.74
Estimated Number of Performance Shares to be Issued	0
Maximum Number of Performance Shares that could Potentially be Issued	32
2010 LTC Plan | Market-Based Performance Condition One
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 12.26
Estimated Number of Performance Shares to be Issued	83
Maximum Number of Performance Shares that could Potentially be Issued	237
2010 LTC Plan | Market-Based Performance Condition Two
Summary of award information associated with market and non-market-based performance condition awards
Grant Date Fair Value	$ 5.57
Estimated Number of Performance Shares to be Issued	2
Maximum Number of Performance Shares that could Potentially be Issued	5