Securities (Details) (USD $)	3 Months Ended
	Sep. 30, 2014 Position	Dec. 31, 2013 Position
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,037,887,000	$ 1,379,751,000
Unrealized gains	12,964,000	14,737,000
Unrealized losses	6,349,000	29,607,000
Estimated fair value	1,044,502,000	1,364,881,000
Amortized costs of securities available for sale pledged to secure public deposits	1,400,000,000	1,400,000,000
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	216,300,000	218,400,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	186,397,000	812,106,000
12 Months or Longer, Fair Value	320,872,000	9,842,000
Total, Fair Value	507,269,000	821,948,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(796,000)	(29,201,000)
12 months or longer Unrealized Losses	(5,553,000)	(406,000)
Total Unrealized Losses	(6,349,000)	(29,607,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	41	314
12 Months or Longer, Number of Positions	73	2
Total, Number of Positions	114	316
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	459,620,000	117,283,000
Unrealized gains	817,000	570,000
Unrealized losses	5,650,000	4,577,000
Estimated fair value	454,787,000	113,276,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	69,899,000	58,468,000
12 Months or Longer, Fair Value	290,934,000	0
Total, Fair Value	360,833,000	58,468,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(216,000)	(4,577,000)
12 Months or Longer, Unrealized Losses	(5,434,000)	0
Total, Unrealized Losses	(5,650,000)	(4,577,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	131	6
12 Months or Longer, Number of Positions	42	0
Total, Number of Positions	173	6
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%
Securities Transfer from AFS to HTM	340,000,000
Unrealized loss on transfer of securities at time of transfer	8,300,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	28,387,000
From one to five years	360,452,000
From five to ten years	174,046,000
After ten years	462,098,000
Total, Amortized Cost	1,024,983,000
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	28,556,000
From one to five years	358,898,000
From five to ten years	176,437,000
After ten years	465,483,000
Total, Fair Value	1,029,374,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Within one year	27,414,000
From one to five years	16,404,000
From five to ten years	84,702,000
After ten years	331,100,000
Amortized cost	459,620,000	117,283,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Within one year	27,530,000
From one to five years	16,551,000
From five to ten years	84,831,000
After ten years	325,875,000
Total, Fair Value	454,787,000	113,276,000
Mortgage-Backed [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	802,000	953,000
Unrealized gains	118,000	128,000
Unrealized losses	0	0
Estimated fair value	920,000	1,081,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	802,000	953,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	920,000	1,081,000
State & Municipal [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	130,845,000	54,305,000
Unrealized gains	538,000	442,000
Unrealized losses	138,000	8,000
Estimated fair value	131,245,000	54,739,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	48,620,000	1,012,000
12 Months or Longer, Fair Value	5,322,000	0
Total, Fair Value	53,942,000	1,012,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(122,000)	(8,000)
12 Months or Longer, Unrealized Losses	(16,000)	0
Total, Unrealized Losses	(138,000)	(8,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	128	1
12 Months or Longer, Number of Positions	19	0
Total, Number of Positions	147	1
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	130,845,000	54,305,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	131,245,000	54,739,000
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	327,973,000	62,025,000
Unrealized gains	161,000	0
Unrealized losses	5,512,000	4,569,000
Estimated fair value	322,622,000	57,456,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	21,279,000	57,456,000
12 Months or Longer, Fair Value	285,612,000	0
Total, Fair Value	306,891,000	57,456,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(94,000)	(4,569,000)
12 Months or Longer, Unrealized Losses	(5,418,000)	0
Total, Unrealized Losses	(5,512,000)	(4,569,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	3	5
12 Months or Longer, Number of Positions	23	0
Total, Number of Positions	26	5
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	327,973,000	62,025,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	322,622,000	57,456,000
US Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	23,079,000	43,279,000
Unrealized gains	134,000	337,000
Unrealized losses	0	0
Estimated fair value	23,213,000	43,616,000
Federal Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	337,254,000	285,880,000
Unrealized gains	301,000	343,000
Unrealized losses	4,238,000	7,308,000
Estimated fair value	333,317,000	278,915,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	51,549,000	233,935,000
12 Months or Longer, Fair Value	226,561,000	9,619,000
Total, Fair Value	278,110,000	243,554,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(191,000)	(6,927,000)
12 months or longer Unrealized Losses	(4,047,000)	(381,000)
Total Unrealized Losses	(4,238,000)	(7,308,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	7	20
12 Months or Longer, Number of Positions	19	1
Total, Number of Positions	26	21
State & Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	40,752,000	113,435,000
Unrealized gains	779,000	1,842,000
Unrealized losses	10,000	1,612,000
Estimated fair value	41,521,000	113,665,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	946,000	50,328,000
12 Months or Longer, Fair Value	2,109,000	0
Total, Fair Value	3,055,000	50,328,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(1,000)	(1,612,000)
12 months or longer Unrealized Losses	(9,000)	0
Total Unrealized Losses	(10,000)	(1,612,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	4	177
12 Months or Longer, Number of Positions	9	0
Total, Number of Positions	13	177
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	62,748,000	143,080,000
12 Months or Longer, Fair Value	47,138,000	0
Total, Fair Value	109,886,000	143,080,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(69,000)	(2,216,000)
12 months or longer Unrealized Losses	(713,000)	0
Total Unrealized Losses	(782,000)	(2,216,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	18	79
12 Months or Longer, Number of Positions	37	0
Total, Number of Positions	55	79
Mortgage-Backed [Member] | Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	349,676,000	337,666,000
Unrealized gains	6,012,000	5,788,000
Unrealized losses	702,000	2,131,000
Estimated fair value	354,986,000	341,323,000
Mortgage-Backed [Member] | U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	18,281,000	21,924,000
Unrealized gains	872,000	1,002,000
Unrealized losses	80,000	85,000
Estimated fair value	19,073,000	22,841,000
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	67,121,000	379,273,000
12 Months or Longer, Fair Value	42,329,000	0
Total, Fair Value	109,450,000	379,273,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(393,000)	(18,243,000)
12 months or longer Unrealized Losses	(684,000)	0
Total Unrealized Losses	(1,077,000)	(18,243,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	9	36
12 Months or Longer, Number of Positions	6	0
Total, Number of Positions	15	36
Collateralized Mortgage Obligations [Member] | Government-sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	211,828,000	521,257,000
Unrealized gains	1,907,000	1,777,000
Unrealized losses	937,000	18,141,000
Estimated fair value	212,798,000	504,893,000
Collateralized Mortgage Obligations [Member] | U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	44,113,000	43,943,000
Unrealized gains	493,000	794,000
Unrealized losses	140,000	102,000
Estimated fair value	44,466,000	44,635,000
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,904,000	12,367,000
Unrealized gains	2,466,000	2,854,000
Unrealized losses	242,000	228,000
Estimated fair value	15,128,000	14,993,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	4,033,000	5,490,000
12 Months or Longer, Fair Value	2,735,000	223,000
Total, Fair Value	6,768,000	5,713,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(142,000)	(203,000)
12 months or longer Unrealized Losses	(100,000)	(25,000)
Total Unrealized Losses	$ (242,000)	$ (228,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	3	2
12 Months or Longer, Number of Positions	2	1
Total, Number of Positions	5	3