Available-for-Sale and Held-to-Maturity Securities (Narrative) (Details) (USD $)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Sep. 30, 2010	Jun. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Fair value of municipal auction rate securites reclassified to AFS		$ 32,900,000
Available-for-sale securities, par value	22,000,000				65,100,000
Gains or losses recorded in consolidated statement of operations		0		0
Principal payments on mortgage-backed securities	43,000,000				164,200,000
Carrying value of municipal auction rate securities from held-to-maturity to available-for-sale		27,800,000
Securities available for sale to securities held to maturity		64,600,000
Unrealized gains, net of deferred taxes	(3,300,000)		100,000		3,300,000	7,600,000
Carrying value of securities pledged as collateral	498,900,000				498,900,000		111,600,000
Available-for-sale securities, Estimated fair value	1,312,784,000				1,312,784,000		1,012,714,000
Available-for-sale securities, percentage of investment portfolio	53.30%				53.30%
Available-for-sale Securities, Amortized cost							1,005,657,000
Credit-related other-than-temporary impairment					1,900,000
Gross unrealized losses related to all other securities							5,004,000	[1]
Available-for-sale Securities [Member]
Available-for-sale securities, Estimated fair value	699,300,000				699,300,000
Available-for-sale Securities, Amortized cost	$ 707,600,000				$ 707,600,000

[1] Unrealized gains/(losses) related to available-for-sale securities are reported in accumulated other comprehensive income/(loss).