Securities (Securities Available for Sale) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,572,523	$ 969,359
Available-for-sale Securities, Gross Unrealized Gain, instant	26,872	38,606
Gross Unrealized Losses	29,744	6,300
Fair Value	1,569,651	1,001,665
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	866,128	561,076
Available-for-sale Securities, Gross Unrealized Gain, instant	12,538	16,719
Gross Unrealized Losses	16,997	5,426
Fair Value	861,669	572,369
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	344,053	265,070
Available-for-sale Securities, Gross Unrealized Gain, instant	13,824	20,893
Gross Unrealized Losses	2,982	388
Fair Value	354,895	285,575
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	335,989	120,085
Available-for-sale Securities, Gross Unrealized Gain, instant	483	851
Gross Unrealized Losses	8,942	435
Fair Value	327,530	120,501
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,074	19,804
Available-for-sale Securities, Gross Unrealized Gain, instant	0	39
Gross Unrealized Losses	657	15
Fair Value	20,417	19,828
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,279	3,324
Available-for-sale Securities, Gross Unrealized Gain, instant	27	104
Gross Unrealized Losses	166	36
Fair Value	$ 5,140	$ 3,392