Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 92,188	$ 90,930	$ 68,014
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	7,550	7,530	4,750
Depreciation, amortization and accretion	4,832	3,091	9,195
Deferred income tax expense	23,461	11,037	13,751
Revaluation of net deferred tax assets due to changes in tax law	14,486	0	0
Funding of mortgage loans held for sale	(1,683,454)	(1,951,144)	(1,483,937)
Proceeds from sales of mortgage loans held for sale	1,775,450	2,031,036	1,647,648
Gains on sales of mortgage loans held for sale	(19,675)	(31,654)	(25,292)
Gains on sales of securities	(148)	(1,186)	(96)
Loss on extinguishment of debt	205	2,539	0
Losses on sales of premises and equipment	565	115	105
Stock-based compensation	5,293	3,117	4,435
Decrease in FDIC loss share indemnification asset, net of accretion and amortization	0	2,891	4,409
Loss on termination of FDIC loss share agreements	0	2,053	0
(Increase) decrease in other assets	(6,620)	10,136	9,463
(Decrease) increase in other liabilities	(12,572)	(16,694)	180
Net cash provided by operating activities	201,561	163,797	252,625
Investing activities
Purchases of securities available for sale	(210,190)	(140,133)	(72,114)
Proceeds from sales of securities available for sale	495,340	4,028	8,444
Proceeds from call/maturities of securities available for sale	169,445	158,359	111,663
Purchases of securities held to maturity	0	(15,267)	(144,027)
Proceeds from sales of securities held to maturity	0	0	0
Proceeds from call/maturities of securities held to maturity	15,882	119,405	145,449
Net increase in loans	(440,205)	(504,640)	(298,676)
Purchases of premises and equipment	(13,047)	(13,560)	(25,165)
Proceeds from sales of premises and equipment	2,101	2,462	2,219
Proceeds from sales of other assets	14,131	16,939	0
Payment made to FDIC to terminate loss share agreements	0	(4,849)	0
Net cash received in acquisition	41,685	25,263	24,776
Net cash provided by (used in) investing activities	75,142	(351,993)	(247,431)
Financing activities
Net increase in noninterest-bearing deposits	11,588	209,943	79,342
Net (decrease) increase in interest-bearing deposits	(88,717)	279,146	(77,124)
Net (decrease) increase in short-term borrowings	(19,862)	(314,952)	375,220
Proceeds from long-term debt	0	98,385	40
Repayment of long-term debt	(170,240)	(47,230)	(308,766)
Cash paid for dividends	(34,416)	(29,734)	(24,557)
Cash received on exercise of stock-based compensation	173	415	102
Excess tax benefits from exercise of stock options	0	2,771	537
Proceeds from equity offering	0	84,105	0
Net cash (used in) provided by financing activities	(301,474)	282,849	44,794
Net (decrease) increase in cash and cash equivalents	(24,771)	94,653	49,988
Cash and cash equivalents at beginning of year	306,224	211,571	161,583
Cash and cash equivalents at end of year	281,453	306,224	211,571
Supplemental disclosures
Cash paid for interest	36,888	25,871	21,615
Cash paid for income taxes	32,556	22,731	18,610
Noncash transactions:
Transfers of loans to other real estate	6,699	8,870	14,935
Financed sales of other real estate owned	773	2,070	1,134
Transfers of loans held for sale to loan portfolio	563	17,838	11,096
Common stock issued in acquisition of businesses	$ 213,590	$ 55,290	$ 281,530