Derivative Financial Instruments - Narrative - Notional Amounts (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Eurodollar Futures [Line Items]
Cash Held by Broker as Margin on Eurodollar Futures Contracts	$ 2,682,000	$ 227,000
[JuniorSubordinatedNotesMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	1.06%	0.57%
Eurodollar Futures Contracts	(578,000)	(983,000)
[JuniorSubordinatedNotesMember] | [Year2013ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.34%	0.34%
Notional Amount	21,000,000	21,000,000
Eurodollar Futures Contracts	(178,000)	(341,000)
[JuniorSubordinatedNotesMember] | [Year2014ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.54%	0.48%
Notional Amount	26,000,000	26,000,000
Eurodollar Futures Contracts	(377,000)	(393,000)
[JuniorSubordinatedNotesMember] | [Year2015ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	1.15%	0.74%
Notional Amount	26,000,000	26,000,000
Eurodollar Futures Contracts	(87,000)	(192,000)
[JuniorSubordinatedNotesMember] | [Year2016ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	2.00%	1.00%
Notional Amount	26,000,000	26,000,000
Eurodollar Futures Contracts	64,000	(57,000)
[JuniorSubordinatedNotesMember] | [ParentCompanyMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	1.06%
Eurodollar Futures Contracts	(578,000)
[JuniorSubordinatedNotesMember] | [ParentCompanyMember] | [Year2013ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.34%
Notional Amount	21,000,000
Eurodollar Futures Contracts	(178,000)
[JuniorSubordinatedNotesMember] | [ParentCompanyMember] | [Year2014ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.54%
Notional Amount	26,000,000
Eurodollar Futures Contracts	(377,000)
[JuniorSubordinatedNotesMember] | [ParentCompanyMember] | [Year2015ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	1.15%
Notional Amount	26,000,000
Eurodollar Futures Contracts	(87,000)
[JuniorSubordinatedNotesMember] | [ParentCompanyMember] | [Year2016ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	2.00%
Notional Amount	26,000,000
Eurodollar Futures Contracts	64,000
[RepurchaseAgreementsHedgedMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	1.82%	0.34%
Eurodollar Futures Contracts	6,172,000	(375,000)
[RepurchaseAgreementsHedgedMember] | [Year2013ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.34%	0.34%
Notional Amount	280,000,000	30,000,000
Eurodollar Futures Contracts	(227,000)	(375,000)
[RepurchaseAgreementsHedgedMember] | [Year2014ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.54%
Notional Amount	250,000,000
Eurodollar Futures Contracts	173,000
[RepurchaseAgreementsHedgedMember] | [Year2015ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	1.15%
Notional Amount	250,000,000
Eurodollar Futures Contracts	890,000
[RepurchaseAgreementsHedgedMember] | [Year2016ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	2.15%
Notional Amount	250,000,000
Eurodollar Futures Contracts	1,989,000
[RepurchaseAgreementsHedgedMember] | [Year2017ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	3.00%
Notional Amount	250,000,000
Eurodollar Futures Contracts	2,219,000
[RepurchaseAgreementsHedgedMember] | [Year2018ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	3.54%
Notional Amount	250,000,000
Eurodollar Futures Contracts	1,128,000
[RepurchaseAgreementsHedgedMember] | [ParentCompanyMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.34%
Eurodollar Futures Contracts	(220,000)
[RepurchaseAgreementsHedgedMember] | [ParentCompanyMember] | [Year2013ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.34%
Notional Amount	30,000,000
Eurodollar Futures Contracts	(220,000)
[RepurchaseAgreementsHedgedMember] | [ParentCompanyMember] | [Year2014ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.00%
Notional Amount	0
Eurodollar Futures Contracts	0
[RepurchaseAgreementsHedgedMember] | [ParentCompanyMember] | [Year2015ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.00%
Notional Amount	0
Eurodollar Futures Contracts	0
[RepurchaseAgreementsHedgedMember] | [ParentCompanyMember] | [Year2016ExpirationMember]
Eurodollar Futures [Line Items]
Locked In Libor Rate	0.00%
Notional Amount	0
Eurodollar Futures Contracts	$ 0