Securities - Unrealized Loss on Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	$ 169,334	$ 412,880
More than 12 months, fair value	42,414	82,017
Total fair value	211,748	494,897
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	826	743
More than 12 months, unrealized loss	707	1,147
Total unrealized loss	1,533	1,890
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	10,955	7,843
More than 12 months, fair value	63,868	109,090
Total fair value	74,823	116,933
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Less than 12 months, unrealized loss	98	31
More than 12 months, unrealized loss	823	1,214
Total unrealized loss	921	1,245
US Treasury
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	0	4,968
More than 12 months, fair value	0	0
Total fair value	0	4,968
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	0	7
More than 12 months, unrealized loss	0	0
Total unrealized loss	0	7
US Government Agency Debentures
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	0	4,828
More than 12 months, fair value	0	0
Total fair value	0	4,828
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	0	7
More than 12 months, unrealized loss	0	0
Total unrealized loss	0	7
State and Political Subdivisions
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	38,943	28,155
More than 12 months, fair value	23,758	44,269
Total fair value	62,701	72,424
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	325	90
More than 12 months, unrealized loss	629	816
Total unrealized loss	954	906
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	10,955	7,843
More than 12 months, fair value	57,230	64,946
Total fair value	68,185	72,789
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Less than 12 months, unrealized loss	98	31
More than 12 months, unrealized loss	791	725
Total unrealized loss	889	756
Other Equity Securities
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	0	6,049
More than 12 months, fair value	0	0
Total fair value	0	6,049
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	0	12
More than 12 months, unrealized loss	0	0
Total unrealized loss	0	12
Residential MBS
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	53,148	347,777
More than 12 months, fair value	18,656	27,632
Total fair value	71,804	375,409
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	119	573
More than 12 months, unrealized loss	78	234
Total unrealized loss	197	807
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	0	0
More than 12 months, fair value	0	0
Total fair value	0	0
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Less than 12 months, unrealized loss	0	0
More than 12 months, unrealized loss	0	0
Total unrealized loss	0	0
Commercial MBS
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	77,243	21,103
More than 12 months, fair value	0	10,116
Total fair value	77,243	31,219
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss [Abstract]
Less than 12 months, unrealized loss	382	54
More than 12 months, unrealized loss	0	97
Total unrealized loss	382	151
Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months, fair value	0	0
More than 12 months, fair value	6,638	44,144
Total fair value	6,638	44,144
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Less than 12 months, unrealized loss	0	0
More than 12 months, unrealized loss	32	489
Total unrealized loss	$ 32	$ 489

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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This item represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized neither as held-to-maturity nor trading securities.

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

-Publisher FASB

-Name Accounting Standards Codification

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

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This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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-Section 50

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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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

-Publisher FASB

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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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Amount of unrealized loss on investments in held-to-maturity securities that have been in a loss position for twelve months or longer.

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Amount of unrealized loss before deducting unrealized gain on investments in held-to-maturity securities that have been in a loss position for less than twelve months.

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

-Publisher FASB

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This item represents the fair value of securities categorized as held-to-maturity securities that have been in a continuous unrealized loss position for twelve months or longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563

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