					Weighted-
					Average Interest
					Rate at
		December 31,			March 31, 2012
		2011		March 31, 2012	(a)
Revolving credit facility	$	—	$	—	—	%
$250.0 million of 6.45% Notes due 2014		249,844		249,859	6.3	%
$250.0 million of 5.65% Notes due 2016		252,037		251,930	5.6	%
$250.0 million of 6.40% Notes due 2018		263,477		262,962	5.3	%
$550.0 million of 6.55% Notes due 2019		578,521		577,665	5.6	%
$550.0 million of 4.25% Notes due 2021		558,932		558,723	4.0	%
$250.0 million of 6.40% Notes due 2037		248,964		248,968	6.4	%
Total debt	$	2,151,775	$	2,150,107	5.3	%

(a) Weighted-average interest rate includes the impact of interest rate swaps, the amortization/accretion of discounts and premiums and the amortization/accretion of gains and losses realized on historical cash flow and fair value hedges (see Note 7—Derivative Financial Instruments for detailed information regarding fair value hedges and interest rate swaps).