Summary of Significant Accounting Policies - Bank Owned Life Insurance (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Bank owned life insurance, cash surrender value	$ 402,100,000	$ 395,800,000
Bank owned life insurance, stabilization reserve	28,700,000	27,600,000
Bank owned life insurance, deferred acquisition costs		$ 1,000us-gaap_DeferredPolicyAcquisitionCosts

Net amount of deferred policy acquisition costs capitalized on contracts remaining in force as of the balance sheet date.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 825

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6487548&loc=d3e32546-158582

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 30

-Section 55

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35755678&loc=d3e11446-158418

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6481648&loc=d3e11198-158413

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.(a),7)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 7

-Article 7

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant