Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 97.9	$ 57.7	$ 188.9	$ 74.0
Available-for-sale securities:
Change in unrealized gains (losses) on available- for-sale securities	5.8	(1.0)	5.6	2.1
Reclassification adjustment for realized net gains on available-for-sale securities included in net income	(0.1)	(0.2)	(0.5)	(0.5)
Net change in unrealized gains (losses) on available-for-sale securities	5.7	(1.2)	5.1	1.6
Cash flow hedges:
Change in unrealized (losses) gains on cash flow hedges	(0.1)	(3.4)	(2.2)	2.6
Reclassification adjustment for realized net (gains) losses on cash flow hedges included in net income	(0.4)	1.5	(1.8)	5.0
Net change in unrealized (losses) gains on cash flow hedges	(0.5)	(1.9)	(4.0)	7.6
Change in foreign currency translation adjustments	(3.7)	(4.5)	(9.5)	0.1
Other comprehensive income (loss), net of tax	1.5	(7.6)	(8.4)	9.3
Comprehensive income	$ 99.4	$ 50.1	$ 180.5	$ 83.3