Securities (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2014 Position	Dec. 31, 2013 Position
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,376,799,000	$ 1,379,751,000
Unrealized gains	18,284,000	14,737,000
Unrealized losses	16,284,000	29,607,000
Estimated fair value	1,378,799,000	1,364,881,000
Sales transactions of securities available for sale [Abstract]
Proceeds from sales	26,200,000
Gross realized gains	1,100,000
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	225,900,000	218,400,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	116,831,000	812,106,000
12 Months or Longer, Fair Value	570,064,000	9,842,000
Total, Fair Value	686,895,000	821,948,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(621,000)	(29,201,000)
12 months or longer Unrealized Losses	(15,663,000)	(406,000)
Total Unrealized Losses	(16,284,000)	(29,607,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	55	314
12 Months or Longer, Number of Positions	150	2
Total, Number of Positions	205	316
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	125,965,000	117,283,000
Unrealized gains	550,000	570,000
Unrealized losses	3,139,000	4,577,000
Estimated fair value	123,376,000	113,276,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value		58,468,000
12 Months or Longer, Fair Value		0
Total, Fair Value		58,468,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses		(4,577,000)
12 Months or Longer, Unrealized Losses		0
Total, Unrealized Losses		(4,577,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions		6
12 Months or Longer, Number of Positions		0
Total, Number of Positions		6
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities. (in hundredths)	10.00%
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	29,964,000
From one to five years	359,226,000
From five to ten years	215,602,000
After ten years	759,045,000
Total, Amortized Cost	1,363,837,000
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	30,109,000
From one to five years	358,895,000
From five to ten years	220,020,000
After ten years	753,985,000
Total, Fair Value	1,363,009,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Within one year	30,983,000
From one to five years	17,462,000
From five to ten years	15,636,000
After ten years	61,884,000
Amortized cost	125,965,000	117,283,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Within one year	31,083,000
From one to five years	17,651,000
From five to ten years	15,772,000
After ten years	58,870,000
Total, Fair Value	123,376,000	113,276,000
State & Municipal [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	65,320,000	54,305,000
Unrealized gains	425,000	442,000
Unrealized losses	0	8,000
Estimated fair value	65,745,000	54,739,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value		1,012,000
12 Months or Longer, Fair Value		0
Total, Fair Value		1,012,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses		(8,000)
12 Months or Longer, Unrealized Losses		0
Total, Unrealized Losses		(8,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions		1
12 Months or Longer, Number of Positions		0
Total, Number of Positions		1
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	65,320,000	54,305,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	65,745,000	54,739,000
Mortgage backed [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	853,000	953,000
Unrealized gains	125,000	128,000
Unrealized losses	0	0
Estimated fair value	978,000	1,081,000
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	853,000	953,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	978,000	1,081,000
Collateralized Mortgage Obligations [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	59,792,000	62,025,000
Unrealized gains	0	0
Unrealized losses	3,139,000	4,569,000
Estimated fair value	56,653,000	57,456,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	56,653,000	57,456,000
12 Months or Longer, Fair Value	0	0
Total, Fair Value	56,653,000	57,456,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(3,139,000)	(4,569,000)
12 Months or Longer, Unrealized Losses	0	0
Total, Unrealized Losses	(3,139,000)	(4,569,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	5	5
12 Months or Longer, Number of Positions	0	0
Total, Number of Positions	5	5
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Amortized cost	59,792,000	62,025,000
Held-to-maturity Securities, Debt Maturities, Fair Value [Abstract]
Total, Fair Value	56,653,000	57,456,000
US Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	33,129,000	43,279,000
Unrealized gains	195,000	337,000
Unrealized losses	0	0
Estimated fair value	33,324,000	43,616,000
Federal Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	310,181,000	285,880,000
Unrealized gains	478,000	343,000
Unrealized losses	3,518,000	7,308,000
Estimated fair value	307,141,000	278,915,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	14,584,000	233,935,000
12 Months or Longer, Fair Value	227,183,000	9,619,000
Total, Fair Value	241,767,000	243,554,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(17,000)	(6,927,000)
12 months or longer Unrealized Losses	(3,501,000)	(381,000)
Total Unrealized Losses	(3,518,000)	(7,308,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	2	20
12 Months or Longer, Number of Positions	19	1
Total, Number of Positions	21	21
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	1,523,000	143,080,000
12 Months or Longer, Fair Value	49,695,000	0
Total, Fair Value	51,218,000	143,080,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(6,000)	(2,216,000)
12 months or longer Unrealized Losses	(516,000)	0
Total Unrealized Losses	(522,000)	(2,216,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	12	79
12 Months or Longer, Number of Positions	36	0
Total, Number of Positions	48	79
Mortgage-Backed [Member] | Government-sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	368,988,000	337,666,000
Unrealized gains	8,473,000	5,788,000
Unrealized losses	428,000	2,131,000
Estimated fair value	377,033,000	341,323,000
Mortgage-Backed [Member] | U.S. government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	19,527,000	21,924,000
Unrealized gains	921,000	1,002,000
Unrealized losses	94,000	85,000
Estimated fair value	20,354,000	22,841,000
State & Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	103,253,000	113,435,000
Unrealized gains	2,267,000	1,842,000
Unrealized losses	172,000	1,612,000
Estimated fair value	105,348,000	113,665,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	8,256,000	50,328,000
12 Months or Longer, Fair Value	20,416,000	0
Total, Fair Value	28,672,000	50,328,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(22,000)	(1,612,000)
12 months or longer Unrealized Losses	(150,000)	0
Total Unrealized Losses	(172,000)	(1,612,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	28	177
12 Months or Longer, Number of Positions	70	0
Total, Number of Positions	98	177
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	89,915,000	379,273,000
12 Months or Longer, Fair Value	269,579,000	0
Total, Fair Value	359,494,000	379,273,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(542,000)	(18,243,000)
12 months or longer Unrealized Losses	(11,333,000)	0
Total Unrealized Losses	(11,875,000)	(18,243,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	12	36
12 Months or Longer, Number of Positions	23	0
Total, Number of Positions	35	36
Collateralized Mortgage Obligations [Member] | Government-sponsored enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	480,694,000	521,257,000
Unrealized gains	2,315,000	1,777,000
Unrealized losses	11,816,000	18,141,000
Estimated fair value	471,193,000	504,893,000
Collateralized Mortgage Obligations [Member] | U.S. government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	48,065,000	43,943,000
Unrealized gains	610,000	794,000
Unrealized losses	59,000	102,000
Estimated fair value	48,616,000	44,635,000
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	12,962,000	12,367,000
Unrealized gains	3,025,000	2,854,000
Unrealized losses	197,000	228,000
Estimated fair value	15,790,000	14,993,000
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	2,553,000	5,490,000
12 Months or Longer, Fair Value	3,191,000	223,000
Total, Fair Value	5,744,000	5,713,000
Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months Unrealized Losses	(34,000)	(203,000)
12 months or longer Unrealized Losses	(163,000)	(25,000)
Total Unrealized Losses	$ (197,000)	$ (228,000)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions	1	2
12 Months or Longer, Number of Positions	2	1
Total, Number of Positions	3	3