Available-for-Sale and Held-to-Maturity Securities (Schedule of Amortized Cost and Fair Values of the Available for Sale Securities and Held to Maturity Securities) (Details) (USD $) In Thousands	Jun. 30, 2011		Dec. 31, 2010
Available-for-sale Securities, Amortized cost	$ 1,056,867		$ 1,005,657
Available-for-sale Securities, Gross unrealized gains	20,878	[1]	12,061	[1]
Available-for-sale Securities, Gross unrealized losses	(3,631)	[1]	(5,004)	[1]
Available-for-sale securities, Estimated fair value	1,074,114		1,012,714
Held-to-maturity Securities, Amortized cost	103,736	[2]	52,640	[2]
Held-to-maturity Securities, Gross unrealized gains	1,671	[1],[2]	4,001	[1],[2]
Held-to-maturity Securities, Gross unrealized losses	(2,775)	[1],[2]	(3,657)	[1],[2]
Held-to-maturity securities, Estimated fair value	102,632	[2]	52,984	[2]
U.S. Government Securities [Member]
Available-for-sale Securities, Amortized cost			24,972
Available-for-sale Securities, Gross unrealized gains			58	[1]
Available-for-sale Securities, Gross unrealized losses			0	[1]
Available-for-sale securities, Estimated fair value			25,030
State and Municipal Securities [Member]
Available-for-sale Securities, Amortized cost	57,750		26,678
Available-for-sale Securities, Gross unrealized gains	3,029	[1]	727	[1]
Available-for-sale Securities, Gross unrealized losses	(554)	[1]	(1,062)	[1]
Available-for-sale securities, Estimated fair value	60,225		26,343
Agency [Member]
Available-for-sale Securities, Amortized cost	560,400		692,922
Available-for-sale Securities, Gross unrealized gains	12,887	[1]	6,938	[1]
Available-for-sale Securities, Gross unrealized losses	(637)	[1]	(2,697)	[1]
Available-for-sale securities, Estimated fair value	572,650		697,163
Commercial [Member]
Available-for-sale Securities, Amortized cost	149,497		66,912
Available-for-sale Securities, Gross unrealized gains	1,318	[1]	1,212	[1]
Available-for-sale Securities, Gross unrealized losses	(668)	[1]	(128)	[1]
Available-for-sale securities, Estimated fair value	150,147		67,996
Non-Agency [Member]
Available-for-sale Securities, Amortized cost	24,539		29,319
Available-for-sale Securities, Gross unrealized gains	591	[1]	744	[1]
Available-for-sale Securities, Gross unrealized losses	(822)	[1]	(790)	[1]
Available-for-sale securities, Estimated fair value	24,308		29,273
Corporate Fixed Income Securities [Member]
Available-for-sale Securities, Amortized cost	237,340		153,523
Available-for-sale Securities, Gross unrealized gains	2,425	[1]	1,705	[1]
Available-for-sale Securities, Gross unrealized losses	(770)	[1]	(327)	[1]
Available-for-sale securities, Estimated fair value	238,995		154,901
Held-to-maturity Securities, Amortized cost	55,593
Held-to-maturity Securities, Gross unrealized gains	0	[1]
Held-to-maturity Securities, Gross unrealized losses	0	[1]
Held-to-maturity securities, Estimated fair value	55,593
Asset-backed Securities [Member]
Available-for-sale Securities, Amortized cost	27,341		11,331
Available-for-sale Securities, Gross unrealized gains	628	[1]	677	[1]
Available-for-sale Securities, Gross unrealized losses	(180)	[1]	0	[1]
Available-for-sale securities, Estimated fair value	27,789		12,008
Held-to-maturity Securities, Amortized cost	29,501	[2]	8,921	[2]
Held-to-maturity Securities, Gross unrealized gains	648	[1],[2]	198	[1],[2]
Held-to-maturity Securities, Gross unrealized losses	(2,775)	[1],[2]	(3,486)	[1],[2]
Held-to-maturity securities, Estimated fair value	27,374	[2]	5,633	[2]
Municipal Auction Rate Securities [Member]
Held-to-maturity Securities, Amortized cost	18,642	[2]	43,719	[2]
Held-to-maturity Securities, Gross unrealized gains	1,023	[1],[2]	3,803	[1],[2]
Held-to-maturity Securities, Gross unrealized losses	0	[1],[2]	(171)	[1],[2]
Held-to-maturity securities, Estimated fair value	$ 19,665	[2]	$ 47,351	[2]

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

[2] Held-to-maturity securities are carried in the consolidated statements of financial condition at amortized cost, and the changes in the value of these securities, other than impairment charges, are not reported on the consolidated financial statements.