Derivatives (Details 3)	Jun. 30, 2012 USD ($)	Jun. 30, 2012 NOK	Dec. 31, 2011 USD ($)
Interest Rate Fair Value Hedges [Abstract]
Notional Amount of Interest Rate Fair Value Hedge Derivatives	$ 600		$ 1,450,000,000
Weighted-average, LIBOR-based, floating rate	4.72%	4.72%
Notional Amount of Foreign Currency Derivatives		3,310,000,000
Derivative, Average Forward Exchange Rate		5.825