Summary of Significant Accounting Policies Earnings Per Share (Details) (USD $)	12 Months Ended						12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Convertible Debt [Member]	Dec. 31, 2013 Convertible Debt [Member]	Dec. 31, 2010 Convertible Debt [Member]	Dec. 31, 2013 Retained Earnings	Dec. 31, 2012 Retained Earnings	Dec. 31, 2011 Retained Earnings
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
Weighted Average Number Diluted Shares Outstanding Adjustment	1,383,000	0	3,809,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	2,102,000	0
Earnings Per Share Reconciliation [Abstract]
Net Income (loss)	$ 170,935,000	$ (54,249,000)	$ 215,416,000				$ 170,935,000	$ (54,249,000)	$ 215,416,000
Weighted Average Number of Shares Outstanding, Basic	66,615,000	65,138,000	63,755,000
Incremental Common Shares Attributable to Share-based Payment Arrangements	1,383,000	0	2,592,000
Incremental Common Shares Attributable to Conversion of Debt Securities	0	0	1,217,000
Weighted Average Number of Shares Outstanding, Diluted	67,998,000	65,138,000	67,564,000
Basic net income (loss) per common share	$ 2.57	$ (0.83)	$ 3.38
Diluted net income (loss) per common share	$ 2.51	$ (0.83)	$ 3.19