Investments Schedule of Available-for-sale and Held-to-Maturity Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 701,824		$ 694,832
Available-for-sale Securities, Gross Unrealized Gains	4,867		4,535
Available-for-sale Securities, Gross Unrealized Losses	(6,160)		(7,638)
Available-for-sale securities at fair value	700,531		691,729
Held-to-maturity Securities	127,938		112,014
Held-to-maturity Securities, Unrecognized Holding Gain	145		15
Held-to-maturity Securities, Unrecognized Holding Loss	(364)		(1,112)
Held-to-maturity Securities, Fair Value	127,719		110,917
US Government and Government Agencies and Authorities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	12,175		2,300
Available-for-sale Securities, Gross Unrealized Gains	3		15
Available-for-sale Securities, Gross Unrealized Losses	(149)		(27)
Available-for-sale securities at fair value	12,029		2,288
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	234,325		228,670
Available-for-sale Securities, Gross Unrealized Gains	308		301
Available-for-sale Securities, Gross Unrealized Losses	(846)		(1,031)
Available-for-sale securities at fair value	233,787		227,940
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	229,103		218,900
Available-for-sale Securities, Gross Unrealized Gains	1,975		1,431
Available-for-sale Securities, Gross Unrealized Losses	(1,265)		(1,898)
Available-for-sale securities at fair value	229,813		218,433
Mortgage Backed Securities, Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	212,615	[1]	229,609	[1]
Available-for-sale Securities, Gross Unrealized Gains	2,284	[1]	2,513	[1]
Available-for-sale Securities, Gross Unrealized Losses	(3,894)	[1]	(4,678)	[1]
Available-for-sale securities at fair value	211,005	[1]	227,444	[1]
Held-to-maturity Securities	127,938	[1]	112,014	[1]
Held-to-maturity Securities, Unrecognized Holding Gain	145	[1]	15	[1]
Held-to-maturity Securities, Unrecognized Holding Loss	(364)	[1]	(1,112)	[1]
Held-to-maturity Securities, Fair Value	127,719	[1]	110,917	[1]
Other Aggregated Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	13,606		15,353
Available-for-sale Securities, Gross Unrealized Gains	297		275
Available-for-sale Securities, Gross Unrealized Losses	(6)		(4)
Available-for-sale securities at fair value	$ 13,897		$ 15,624

[1] All mortgage-backed securities are guaranteed by U.S. government agencies or Government-sponsored entities.