Securities, Available for Sale (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) Position	Dec. 31, 2015 USD ($) Position	Dec. 31, 2014 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 1,341,059	$ 1,169,337
Unrealized gains	11,097	9,878
Unrealized losses	13,866	4,671
Estimated fair value	1,338,290	1,174,544
Amortized costs of securities available for sale pledged to secure public deposits	1,500,000	1,400,000
Amortized costs of securities available for sale pledged as collateral for repurchase agreements	235,600
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	902,506	624,819
12 Months or Longer, Fair Value	5,831	29,822
Total, Fair Value	908,337	654,641
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(12,347)	(4,283)
12 Months or Longer, Unrealized Losses	(1,519)	(388)
Total Unrealized Losses	$ (13,866)	$ (4,671)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions | Position	171	79
12 Months or Longer, Number of Positions | Position	7	12
Total, Number of Positions | Position	178	91
Sales transactions of securities available for sale [Abstract]
Gross realized gains	$ 683	$ 3,099	$ 49
Gross realized losses	(1,327)	(12)	0
Net securities (losses) gains	(644)	3,087	49
Gains from calls on securities available for sale	100	$ 100	$ 100
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Within one year	67,803
From one to five years	162,913
From five to ten years	144,957
After ten years	949,537
Total, Amortized Cost	1,325,210
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract]
Within one year	67,877
From one to five years	162,754
From five to ten years	146,014
After ten years	940,906
Total, Fair Value	$ 1,317,551
Consolidated stockholders' equity threshold percentage that no single issuer of securities exceeded except for U.S. Government securities	10.00%	10.00%
Federal Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 175,135	$ 312,580
Unrealized gains	78	203
Unrealized losses	805	1,511
Estimated fair value	174,408	311,272
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	119,363	186,685
12 Months or Longer, Fair Value	0	19,801
Total, Fair Value	119,363	206,486
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(805)	(1,312)
12 Months or Longer, Unrealized Losses	0	(199)
Total Unrealized Losses	$ (805)	$ (1,511)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions | Position	10	15
12 Months or Longer, Number of Positions | Position	0	2
Total, Number of Positions | Position	10	17
State & Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 47,053	$ 31,208
Unrealized gains	153	446
Unrealized losses	480	17
Estimated fair value	46,726	31,637
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	31,873	4,599
12 Months or Longer, Fair Value	483	502
Total, Fair Value	32,356	5,101
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(478)	(14)
12 Months or Longer, Unrealized Losses	(2)	(3)
Total Unrealized Losses	$ (480)	$ (17)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions | Position	55	7
12 Months or Longer, Number of Positions | Position	1	1
Total, Number of Positions | Position	56	8
Mortgage-Backed [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	$ 277,524	$ 177,270
12 Months or Longer, Fair Value	985	1,066
Total, Fair Value	278,509	178,336
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(2,668)	(1,068)
12 Months or Longer, Unrealized Losses	(13)	(14)
Total Unrealized Losses	$ (2,681)	$ (1,082)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions | Position	49	33
12 Months or Longer, Number of Positions | Position	4	5
Total, Number of Positions | Position	53	38
Mortgage-backed Securities, Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 513,814	$ 398,086
Unrealized gains	3,345	4,141
Unrealized losses	2,492	1,068
Estimated fair value	514,667	401,159
Mortgage-backed Securities, U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	14,955	8,191
Unrealized gains	411	560
Unrealized losses	189	14
Estimated fair value	15,177	8,737
Collateralized Mortgage Obligations [Member]
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	473,746	256,265
12 Months or Longer, Fair Value	0	5,218
Total, Fair Value	473,746	261,483
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	(8,396)	(1,889)
12 Months or Longer, Unrealized Losses	0	(54)
Total Unrealized Losses	$ (8,396)	$ (1,943)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions | Position	57	24
12 Months or Longer, Number of Positions | Position	0	2
Total, Number of Positions | Position	57	26
Collateralized Mortgage Obligations, Government-Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 513,431	$ 364,936
Unrealized gains	532	931
Unrealized losses	7,688	1,828
Estimated fair value	506,275	364,039
Collateralized Mortgage Obligations, U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	60,822	40,699
Unrealized gains	184	348
Unrealized losses	708	115
Estimated fair value	60,298	40,932
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	15,849	13,637
Unrealized gains	6,394	3,249
Unrealized losses	1,504	118
Estimated fair value	20,739	16,768
Unrealized Loss Position, Fair Value [Abstract]
Less Than 12 Months, Fair Value	0	0
12 Months or Longer, Fair Value	4,363	3,235
Total, Fair Value	4,363	3,235
Unrealized Loss Position, Unrealized Losses [Abstract]
Less Than 12 Months, Unrealized Losses	0	0
12 Months or Longer, Unrealized Losses	(1,504)	(118)
Total Unrealized Losses	$ (1,504)	$ (118)
Unrealized Loss Position, Number of Positions [Abstract]
Less Than 12 Months, Number of Positions | Position	0	0
12 Months or Longer, Number of Positions | Position	2	2
Total, Number of Positions | Position	2	2