Investments in Non-Consolidated Affiliates (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended				12 Months Ended
	Mar. 31, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012
Investments in Non-Consolidated Affiliates
Initial payment received from the sale of the joint venture	$ 37.6				$ 37.6
Installment payments received from the sale of the joint venture		4.6	4.8	4.7		14.1
Expected proceeds from the sale of the joint ventures		$ 57				$ 57
PIGAP II
Ownership interest of each equity method investee
Ownership Interest (as a percent)		30.00%				30.00%
El Furrial
Ownership interest of each equity method investee
Ownership Interest (as a percent)		33.30%				33.30%