Investments (Details 1) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Investment Securities, Available-for-sale
Amortized Cost	$ 1,517,425	$ 1,500,516
Gross Unrealized Gains	43,453	27,774
Gross Unrealized Losses	8,763	33,545
Available-for-sale, at fair value	1,552,115	1,494,745
Municipal securities
Investment Securities, Available-for-sale
Amortized Cost	453,890	459,182
Gross Unrealized Gains	9,286	1,749
Gross Unrealized Losses	6,610	24,273
Available-for-sale, at fair value		436,658
Corporate Debt Securities [Member]
Investment Securities, Available-for-sale
Amortized Cost	107,669	84,119
Gross Unrealized Gains	1,789	71
Gross Unrealized Losses	67	1,483
Available-for-sale, at fair value		82,707
US Government-sponsored Enterprises Debt Securities [Member]
Investment Securities, Available-for-sale
Amortized Cost	36,198	10,046
Gross Unrealized Gains	467	0
Gross Unrealized Losses	0	174
Available-for-sale, at fair value		9,872
Other securities [Member]
Investment Securities, Available-for-sale
Amortized Cost	26,301	27,654
Gross Unrealized Gains	45	2
Gross Unrealized Losses	24	113
Available-for-sale, at fair value		27,543
Residential Mortgage Backed Securities [Member] | Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Investment Securities, Available-for-sale
Amortized Cost	286,347	197,069
Gross Unrealized Gains	2,766	388
Gross Unrealized Losses	1,509	4,584
Available-for-sale, at fair value		192,873
Residential Mortgage Backed Securities [Member] | Government agency and government-sponsored enterprise pass through securities
Investment Securities, Available-for-sale
Amortized Cost	563,820	691,944
Gross Unrealized Gains	21,382	18,012
Gross Unrealized Losses	445	2,768
Available-for-sale, at fair value		707,188
Residential Mortgage Backed Securities [Member] | Covered private label collateralized mortgage obligation [Member]
Investment Securities, Available-for-sale
Amortized Cost	28,913	30,502
Gross Unrealized Gains	7,709	7,552
Gross Unrealized Losses	100	(150)
Available-for-sale, at fair value		37,904
Residential Mortgage Backed Securities [Member] | Collateralized Mortgage Obligations [Member]
Investment Securities, Available-for-sale
Amortized Cost	14,287	0
Gross Unrealized Gains	9	0
Gross Unrealized Losses	8	0
Available-for-sale, at fair value		$ 0