Securities Available For Sale (Narrative) (Detail) (Auction Rate Securities [Member], USD $) In Millions, unless otherwise specified	6 Months Ended	39 Months Ended		6 Months Ended								0 Months Ended		6 Months Ended		42 Months Ended		3 Months Ended	42 Months Ended
	Jun. 30, 2013	Dec. 31, 2012		Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member]	Jun. 30, 2013 Asset-backed Securities [Member]		Dec. 31, 2012 Asset-backed Securities [Member]		Jun. 30, 2013 Asset-backed Securities [Member] Minimum [Member] Y	Jun. 30, 2013 Asset-backed Securities [Member] Maximum [Member] Y	Dec. 31, 2012 Collateralized Debt Obligations [Member]		Jun. 30, 2013 Collateralized Debt Obligations [Member] Minimum [Member]	Jun. 30, 2013 Collateralized Debt Obligations [Member] Maximum [Member]	Mar. 31, 2013 Securities Redeemed or Sold [Member]	Mar. 31, 2013 Securities Redeemed or Sold [Member] Other Comprehensive Income (Loss) [Member]	Jun. 30, 2013 Securities Redeemed or Sold [Member] Asset-backed Securities [Member]	Mar. 31, 2013 Securities Redeemed or Sold [Member] Asset-backed Securities [Member]	Mar. 31, 2013 Securities Redeemed or Sold [Member] Collateralized Debt Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Auction rate securities, sold at par																		$ 2.6
Auction rate securities, par value	10.3	17.9														7.6			2.6	5.0
Adjusted cost basis		14.6	[1]			10.3	[1]	12.9	[1]			1.7	[1]			4.3			2.6	1.7
Investment, debt security, default rate of underlying assets												6.22%		8.00%	9.00%
Available-for-sale securities, gross unrealized gain (loss)		(0.2)														1.1	0.7		(0.2)	1.3
Deferred tax liabilities, tax deferred income																0.4
Auction-rate securities yield rate				1.46%	1.92%
Cumulative credit and other losses recognized in earnings	$ 0	$ 3.3														$ 3.3			$ 0	$ 3.3
Contractual maturities of securities, in years										15	34

[1] Adjusted cost basis reflects adjustments for credit and other losses recognized in earnings on our structured finance security. There were no adjustments to the cost basis of securities held as of June 30, 2013. Cumulative adjustments to the cost basis of securities held as of December 31, 2012 totaled $3.3 million. Par value of securities held as of June 30, 2013 and December 31, 2012 totaled $10.3 million and $17.9 million, respectively.