Contractual Commitments, Contingencies, And Off-Balance Sheet Arrangements (Narrative) (Details) (USD $) In Millions	12 Months Ended							12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2009	Jun. 30, 2011 IT Services Agreement [Member]	Jun. 30, 2010 IT Services Agreement [Member]	Jun. 30, 2011 Automatic Data Processing [Member]	Jun. 30, 2011 Maintenance Costs [Member]
Expenses recorded related to agreement					$ 110.4	$ 104.8	$ 102.8				$ 8.9
Expiration date on agreement								June 2012		June 30, 2012
Commitments under agreement	113.4							563.3
Outstanding letter of credit					0.7
Total expenses on agreements		$ 181.3	$ 162.1	$ 152.2				$ 6.3	$ 12.0