Securities Available for Sale and Held to Maturity (1) (Details) (USD $)	3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended																		3 Months Ended
	Dec. 31, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Available for Sale [Member]	Sep. 30, 2013 Available for Sale [Member]	Sep. 30, 2014 Available for Sale [Member]	Sep. 30, 2013 Available for Sale [Member]	Sep. 30, 2014 U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]	Dec. 31, 2013 U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]	Sep. 30, 2014 U.S. Government Agency Obligations Issued by U.S. Government Sponsored Agencies [Member]	Dec. 31, 2013 U.S. Government Agency Obligations Issued by U.S. Government Sponsored Agencies [Member]	Sep. 30, 2014 Obligations of States and Political Subdivisions [Member]	Dec. 31, 2013 Obligations of States and Political Subdivisions [Member]	Sep. 30, 2014 Residential Mortgage Pass Through Securities Guaranteed by GNMA [Member]	Dec. 31, 2013 Residential Mortgage Pass Through Securities Guaranteed by GNMA [Member]	Sep. 30, 2014 Residential Mortgage Pass Through Securities Issued by FNMA and FHLMC [Member]	Dec. 31, 2013 Residential Mortgage Pass Through Securities Issued by FNMA and FHLMC [Member]	Sep. 30, 2014 Other Residential Mortgage Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Dec. 31, 2013 Other Residential Mortgage Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Sep. 30, 2014 Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Dec. 31, 2013 Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]	Sep. 30, 2014 Asset-Backed Securities and Structured Financial Products [Member]	Dec. 31, 2013 Asset-Backed Securities and Structured Financial Products [Member]	Mar. 31, 2014 Collateralized Loan Obligations [Member]
Estimated Fair Value [Abstract]
Estimated Fair Value, Less than 12 Months	$ 2,108,340,000	$ 930,571,000						$ 22,911,000	$ 68,908,000	$ 14,333,000	$ 138,478,000	$ 2,286,000	$ 55,963,000	$ 6,007,000	$ 14,732,000	$ 36,918,000	$ 118,466,000	$ 820,242,000	$ 1,534,381,000	$ 27,874,000	$ 177,412,000
Estimated Fair Value, 12 Months or More	24,415,000	537,616,000						31,307,000	0	9,940,000	0	4,710,000	796,000	675,000	161,000	0	0	420,054,000	23,458,000	70,930,000	0
Estimated Fair Value, Total	2,132,755,000	1,468,187,000						54,218,000	68,908,000	24,273,000	138,478,000	6,996,000	56,759,000	6,682,000	14,893,000	36,918,000	118,466,000	1,240,296,000	1,557,839,000	98,804,000	177,412,000
Gross Unrealized (Losses) [Abstract]
Gross Unrealized (Losses), Less than 12 Months	(47,362,000)	(8,973,000)						(147,000)	(1,485,000)	(55,000)	(2,101,000)	(7,000)	(586,000)	(25,000)	(155,000)	(121,000)	(2,071,000)	(8,173,000)	(36,750,000)	(445,000)	(4,214,000)
Gross Unrealized (Losses), 12 Months or More	(426,000)	(16,865,000)						(925,000)	0	(40,000)	0	(34,000)	(10,000)	(5,000)	(1,000)	0	0	(14,425,000)	(415,000)	(1,436,000)	0
Gross Unrealized (Losses), Total	(47,788,000)	(25,838,000)						(1,072,000)	(1,485,000)	(95,000)	(2,101,000)	(41,000)	(596,000)	(30,000)	(156,000)	(121,000)	(2,071,000)	(22,598,000)	(37,165,000)	(1,881,000)	(4,214,000)
Reclassification of Securities available for sale to securities held to maturity	1,099,000,000
Net unrealized holding loss on AFS Securities at date of transfer	46,600,000
Net unrealized holding loss on AFS Securities, net of tax at date of transfer	28,800,000
Net unamortized, unrealized loss on transfer of securities		41,900,000
Net unamortized, unrealized loss on transfer of securities, net of tax		25,900,000
Sale of collateralized loan obligations																								25,900,000
Net gain on sale of collateralized loan obligations																								389,000
Gain (Loss) on Investments [Line Items]
Other-than-temporary impairments		0	0
Gains (losses) on Investments [Abstract]
Proceeds from calls and sales of securities				30,540,000	0	56,815,000	64,778,000
Gross realized gains				67,000	0	456,000	394,000
Gross realized losses				(156,000)	0	(156,000)	(16,000)
Securities Available for Sale, Amortized Cost [Abstract]
Due in one year or less		15,979,000
Due after one year through five years		119,935,000
Due after five years through ten years		83,488,000
Due after ten years		86,606,000
Total amortized cost, before mortgage-backed securities		306,008,000
Mortgage-backed securities		2,043,623,000
Total, securities available for sale, amortized cost		2,349,631,000
Securities Available for Sale, Estimated Fair Value [Abstract]
Due in one year or less		16,132,000
Due after one year through five years		124,331,000
Due after five years through ten years		86,120,000
Due after ten years		86,285,000
Total, estimated fair value, before mortgage-backed securities		312,868,000
Mortgage-backed securities		2,051,027,000
Securities available for sale	2,194,154,000	2,363,895,000
Securities Held to Maturity, Amortized Cost [Abstract]
Due in one year or less		3,194,000
Due after one year through five years		11,661,000
Due after five years through ten years		134,637,000
Due after ten years		15,813,000
Total, amortized cost, before mortgage-backed securities		165,305,000
Mortgage-backed securities		1,004,335,000
Amortized cost	1,168,728,000	1,169,640,000						0	0	100,767,000	100,159,000	64,538,000	65,987,000	13,368,000	9,433,000	11,816,000	12,724,000	836,966,000	837,393,000	142,185,000	143,032,000	0	0
Securities Held to Maturity, Estimated Fair Value [Abstract]
Due in one year or less		3,220,000
Due after one year through five years		12,394,000
Due after five years through ten years		138,486,000
Due after ten years		16,495,000
Total, estimated fair value, before mortgage-backed securities		170,595,000
Mortgage-backed securities		999,618,000
Total, securities held to maturity, estimated fair value	$ 1,150,833,000	$ 1,170,213,000						$ 0	$ 0	$ 102,570,000	$ 98,579,000	$ 68,025,000	$ 68,512,000	$ 13,657,000	$ 9,503,000	$ 12,061,000	$ 12,592,000	$ 832,583,000	$ 822,321,000	$ 141,317,000	$ 139,326,000	$ 0	$ 0