Long-Term Debt (Details 1) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 1,308
Tax Exempt Revenue Bonds [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.35%
Debt Instrument, Face Amount	31
Mortgages [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.90%
Debt Instrument, Face Amount	250
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	300
Mortgages 1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.31%
Debt Instrument, Face Amount	102
Mortgages 2 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.46%
Debt Instrument, Face Amount	77
Tax-Exempt Revenue Bonds 1 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.13%
Debt Instrument, Face Amount	82
Mortgages 3 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.67%
Debt Instrument, Face Amount	46
mortgages 4 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.50%
Debt Instrument, Face Amount	140
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Debt Instrument, Face Amount	$ 280