Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Numerator:
Net income (loss)	$ 220,053	$ 2,281,884	$ 36,417	$ 81,762	$ 58,742	$ 116,633	$ 42,436	$ (11,666)	$ 2,620,116	[1]	$ 206,145	[1]	$ (210,388)
Less: earnings distributed to participating securities									(407)		0		0
Less: undistributed earnings allocated to participating securities									(19,201)		0		0
Numerator for basic earnings per share									2,600,508		206,145		(210,388)
Add back: undistributed earnings allocated to participating securities									19,201		0		0
Less: undistributed earnings reallocated to participating securities									(18,845)		0		0
Numerator for diluted earnings per share									$ 2,600,864		$ 206,145		$ (210,388)
Denominator:
Basic shares outstanding	379,879	382,883	385,389	384,228	383,404	381,355	380,655	380,502	383,077		381,562		379,877
Effect of dilutive securities									3,789		3,002		0
Diluted shares outstanding	383,724	386,103	391,180	390,321	389,304	384,570	382,203	380,502	386,866		384,564		379,877
Earnings per share:
Basic (usd per share)	$ 0.58	$ 5.92	$ 0.09	$ 0.21	$ 0.15	$ 0.31	$ 0.11	$ (0.03)	$ 6.79		$ 0.54		$ (0.55)
Diluted (usd per share)	$ 0.57	$ 5.87	$ 0.09	$ 0.21	$ 0.15	$ 0.30	$ 0.11	$ (0.03)	$ 6.72		$ 0.54		$ (0.55)

[1] Due to rounding, the sum of quarterly results may not equal the total for the year. Additionally, quarterly and year-to-date computations of per share amounts are made independently.