Securities Available for Sale and Held to Maturity (1) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended			3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Available for Sale [Member]	Sep. 30, 2012 Available for Sale [Member]	Sep. 30, 2013 Available for Sale [Member]	Sep. 30, 2012 Available for Sale [Member]	Sep. 30, 2013 Held to Maturity [Member]	Sep. 30, 2012 Held to Maturity [Member]	Sep. 30, 2013 Held to Maturity [Member]	Sep. 30, 2012 Held to Maturity [Member]	Sep. 30, 2013 U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]	Dec. 31, 2012 U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]	Sep. 30, 2013 U.S. Government Agency Obligations Issued by U.S. Government Sponsored Agencies [Member]	Dec. 31, 2012 U.S. Government Agency Obligations Issued by U.S. Government Sponsored Agencies [Member]	Sep. 30, 2013 Obligations of States and Political Subdivisions [Member]	Dec. 31, 2012 Obligations of States and Political Subdivisions [Member]	Sep. 30, 2013 Residential Mortgage Pass Through Securities Guaranteed by GNMA [Member]	Dec. 31, 2012 Residential Mortgage Pass Through Securities Guaranteed by GNMA [Member]	Sep. 30, 2013 Residential Mortgage Pass Through Securities Issued by FNMA and FHLMC [Member]	Dec. 31, 2012 Residential Mortgage Pass Through Securities Issued by FNMA and FHLMC [Member]	Sep. 30, 2013 Other Residential Mortgage Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Dec. 31, 2012 Other Residential Mortgage Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Sep. 30, 2013 Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Dec. 31, 2012 Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Sep. 30, 2013 Asset-Backed Securities and Structured Financial Products [Member]	Dec. 31, 2012 Asset-Backed Securities and Structured Financial Products [Member]
Estimated Fair Value [Abstract]
Estimated Fair Value, Less than 12 Months	$ 1,829,117		$ 25,345									$ 60,939		$ 132,140		$ 27,414	$ 5,878	$ 36,322		$ 49,792		$ 1,352,905	$ 3,055	$ 153,092	$ 0	$ 16,513	$ 16,412
Estimated Fair Value, 12 Months or More	937		16,339									0		0		569	0	0		0		368	0	0	16,339	0	0
Estimated Fair Value, Total	1,830,054		41,684									60,939		132,140		27,983	5,878	36,322		49,792		1,353,273	3,055	153,092	16,339	16,513	16,412
Gross Unrealized (Losses) [Abstract]
Gross Unrealized (Losses), Less than 12 Months	(67,031)		(57)									(1,370)		(6,536)		(636)	(16)	(1,093)		(663)		(50,293)	(20)	(6,428)	0	(12)	(21)
Gross Unrealized (Losses), 12 Months or More	(4)		(154)									0		0		(1)	0	0		0		(3)	0	0	(154)	0	0
Gross Unrealized (Losses), Total	(67,035)		(211)									(1,370)		(6,536)		(637)	(16)	(1,093)		(663)		(50,296)	(20)	(6,428)	(154)	(12)	(21)
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairments	0	0
Gains (losses) on investments [Abstract]
Proceeds from calls and sales of securities				0	2,710	64,778	37,536	0	0	0	175
Gross realized gains				0	0	394	1,050
Gross realized (losses)				0	(1)	(16)	(12)
Gross realized gains								0	0	0	3
Securities Available for Sale, Amortized Cost [Abstract]
Due in one year or less	10,080
Due after one year through five years	244,598
Due after five years through ten years	271,029
Due after ten years	178,780
Total amortized cost, before mortgage-backed securities	704,487
Mortgage-backed securities	2,693,353
Total, securities available for sale, amortized cost	3,397,840
Securities Available for Sale, Estimated Fair Value [Abstract]
Due in one year or less	10,142
Due after one year through five years	248,610
Due after five years through ten years	270,117
Due after ten years	177,791
Total, estimated fair value, before mortgage-backed securities	706,660
Mortgage-backed securities	2,665,441
Total, securities available for sale, estimated fair value	3,372,101		2,657,745
Securities Held to Maturity, Amortized Cost [Abstract]
Due in one year or less	1,627
Due after one year through five years	13,744
Due after five years through ten years	14,104
Due after ten years	754
Total, amortized cost, before mortgage-backed securities	30,229
Mortgage-backed securities	39,751
Total, securities held to maturity, amortized cost	69,980		42,188									0	0	0	0	30,229	36,206	2,420	3,245	564	572	0	0	36,767	2,165	0	0
Securities Held to Maturity, Estimated Fair Value [Abstract]
Due in one year or less	1,650
Due after one year through five years	14,789
Due after five years through ten years	15,974
Due after ten years	790
Total, estimated fair value, before mortgage-backed securities	33,203
Mortgage-backed securities	37,746
Total, securities held to maturity, estimated fair value	$ 70,949		$ 46,888									$ 0	$ 0	$ 0	$ 0	$ 33,203	$ 40,390	$ 2,578	$ 3,472	$ 599	$ 624	$ 0	$ 0	$ 34,569	$ 2,402	$ 0	$ 0