Summary of Significant Accounting Policies Earnings Per Share (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number Diluted Shares Outstanding Adjustment	0	3,809,000	1,720,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	2,102,000	0	0
Earnings Per Share Reconciliation [Abstract]
Net Income (loss)	$ (54,249,000)	$ 215,416,000	$ 196,837,000
Weighted Average Number of Shares Outstanding, Basic	65,138,000	63,755,000	62,969,000
Incremental Common Shares Attributable to Share-based Payment Arrangements	0	2,592,000	1,720,000
Incremental Common Shares Attributable to Conversion of Debt Securities	0	1,217,000	0
Weighted Average Number of Shares Outstanding, Diluted	65,138,000	67,564,000	64,689,000
Basic net income (loss) per common share	$ (0.83)	$ 3.38	$ 3.13
Diluted net income (loss) per common share	$ (0.83)	$ 3.19	$ 3.04
Convertible Debt [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.50%	3.50%	3.50%
Debt instrument convertible conversion rate	864,106
Debt Instrument, Principal Amount Denominator for Conversion into Common Stock	$ 1,000
Debt Instrument, Convertible, Conversion Price	$ 54.42