Debt Interest Expense and Other Debt Information (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended										12 Months Ended
	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010		Jun. 30, 2012 6.5% Senior Notes [Member]	Jun. 30, 2012 6.25% Senior Notes [Member]	Jun. 30, 2012 8.25% Senior Notes [Member]	Jun. 30, 2012 Senior Notes [Member] 6.25% Interest Rate [Member]	Mar. 31, 2012 Senior Notes [Member] 6.25% Interest Rate [Member]	Dec. 31, 2012 Amortization discount and deferred debt issuance costs [Member]	Dec. 31, 2011 Amortization discount and deferred debt issuance costs [Member]	Dec. 31, 2010 Amortization discount and deferred debt issuance costs [Member]	Dec. 31, 2012 Commitment Fees [Member]	Dec. 31, 2011 Commitment Fees [Member]	Dec. 31, 2010 Commitment Fees [Member]	Dec. 31, 2012 Long-term Debt [Member] Credit Agreement [Member]	Dec. 31, 2011 Long-term Debt [Member] Credit Agreement [Member]	Dec. 31, 2010 Long-term Debt [Member] Credit Agreement [Member]	Dec. 31, 2012 Long-term Debt [Member] Senior Notes [Member] 6.5% Senior Notes [Member]	Dec. 31, 2011 Long-term Debt [Member] Senior Notes [Member] 6.5% Senior Notes [Member]	Dec. 31, 2010 Long-term Debt [Member] Senior Notes [Member] 6.5% Senior Notes [Member]	Dec. 31, 2012 Long-term Debt [Member] Senior Notes [Member] 6.25% Senior Notes [Member]	Dec. 31, 2011 Long-term Debt [Member] Senior Notes [Member] 6.25% Senior Notes [Member]	Dec. 31, 2010 Long-term Debt [Member] Senior Notes [Member] 6.25% Senior Notes [Member]	Dec. 31, 2012 Long-term Debt [Member] Senior Notes [Member] 8.25% Senior Notes [Member]	Dec. 31, 2011 Long-term Debt [Member] Senior Notes [Member] 8.25% Senior Notes [Member]	Dec. 31, 2010 Long-term Debt [Member] Senior Notes [Member] 8.25% Senior Notes [Member]	Dec. 31, 2012 Long-term Debt [Member] Promissory Notes [Member]	Dec. 31, 2011 Long-term Debt [Member] Promissory Notes [Member]	Dec. 31, 2010 Long-term Debt [Member] Promissory Notes [Member]
Debt Instrument [Line Items]
Interest expense, debt		$ 47,459	$ 36,850		$ 34,456							$ 1,946	$ 1,212	$ 713	$ 621	$ 430	$ 392	$ 8,736	$ 10,477	$ 9,109	$ 15,716	$ 0	$ 0	$ 2,422	$ 11,565	$ 11,404	$ 12,380	$ 12,380	$ 10,298	$ 543	$ 745	$ 0
Cash Flow Hedge Loss Reclassified to Earnings		0	0	[1]	(1,076)	[1]
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments		0	0		1,464
Amortization of Unrecognized Loss on Cash Flow Hedge		5,095	41		0
Less capitalized interest		277	891		(462)
Net interest expense		47,182	35,959	[1]	33,994	[1]
Cash paid for interest		38,476	34,825		31,305
Loss on early extinguishment of debt		(2,979)	0	[1]	0	[1]
Stated interest rate, senior notes							6.50%	6.25%	8.25%	6.25%	6.25%
Repayments of senior notes	$ 185,000	$ (260,235)

[1] (1) Restated as described in Note 2.