Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net income	$ 437	$ 441	$ 376
Other comprehensive income:
Net change in unrealized gain (losses) on investments, net of tax of $—, $— and $(1)	0	0	(2)
Benefit obligations, net of tax of $(2), $— and $(1)	(4)	0	(2)
Comprehensive income	$ 433	$ 441	$ 372