Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	$ 4,401,345	$ 1,445,721
Securities available for sale, Gross Unrealized Gains	98,561	51,701
Securities available for sale, Gross Unrealized Losses	3,006	8,537
Securities available for sale, Fair Value	4,496,900	1,488,885
U.S. Treasury [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	150	10,797
Securities available for sale, Gross Unrealized Gains	14	52
Securities available for sale, Gross Unrealized Losses	0	5
Securities available for sale, Fair Value	164	10,844
U.S. government agencies [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	248,595	106,054
Securities available for sale, Gross Unrealized Gains	1,308	971
Securities available for sale, Gross Unrealized Losses	0	434
Securities available for sale, Fair Value	249,903	106,591
Municipal obligations [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	294,489	181,747
Securities available for sale, Gross Unrealized Gains	15,218	4,107
Securities available for sale, Gross Unrealized Losses	42	5,411
Securities available for sale, Fair Value	309,665	180,443
Mortgage-backed securities [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	2,422,891	761,704
Securities available for sale, Gross Unrealized Gains	58,150	38,032
Securities available for sale, Gross Unrealized Losses	696	50
Securities available for sale, Fair Value	2,480,345	799,686
Collateralized mortgage obligations [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	1,426,495	367,662
Securities available for sale, Gross Unrealized Gains	21,774	6,880
Securities available for sale, Gross Unrealized Losses	2,193	2,491
Securities available for sale, Fair Value	1,446,076	372,051
Other debt securities [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	4,517	14,329
Securities available for sale, Gross Unrealized Gains	11	999
Securities available for sale, Gross Unrealized Losses	34	43
Securities available for sale, Fair Value	4,494	15,285
Other equity securities [Member]
Amortized cost and fair value of securities
Securities available for sale, Amortized Cost	4,208	3,428
Securities available for sale, Gross Unrealized Gains	2,086	660
Securities available for sale, Gross Unrealized Losses	41	103
Securities available for sale, Fair Value	$ 6,253	$ 3,985

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15E

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15D

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS115-1/124-1

-Paragraph 15C

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 16

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

+ Details

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details