Consolidated Statements of Cash Flows (Parenthetical)	Dec. 31, 2011 5.5% Term Bond [Member] Term Bonds [Member]	Dec. 31, 2013 7.50% Notes [Member] Convertible Notes Payable [Member]	Dec. 31, 2011 4.5% Convertible Notes [Member] Convertible Notes Payable [Member]
Stated interest rate (percent)	5.50%	7.50%	4.50%