Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands		Total	Stock options	Common stock	Common stock Stock options	Additional paid-in capital	Additional paid-in capital Stock options	Retained earnings	Accumulated other comprehensive income (loss)
Beginning balance at Dec. 31, 2015		$ 1,015,974		$ 38,168		$ 725,280		$ 281,558	$ (29,032)
Changes in Stockholders' Equity
Comprehensive income		64,754						60,864	3,890
Cash dividends declared and paid, $0.82 and $0.79 per share at September 30, 2017 and 2016, respectively		(30,293)						(30,293)
Issuance of common stock and common stock equivalents in business combinations		1,504,811		32,074		1,472,737
Net shares issued under share-based compensation plans			$ 1,966		$ 255		$ 1,711
Share-based compensation expense		6,454		0		6,454
Ending balance at Sep. 30, 2016		2,563,666		70,497		2,206,182		312,129	(25,142)
Beginning balance at Jun. 30, 2016									(25,698)
Changes in Stockholders' Equity
Comprehensive income		12,040
Ending balance at Sep. 30, 2016		2,563,666		70,497		2,206,182		312,129	(25,142)
Changes in Stockholders' Equity
Cumulative effect adjustment of change in accounting policy, net of tax impact	[1]	3,659						3,659
Beginning balance at Dec. 31, 2016		2,581,526		70,599		2,210,762		340,201	(40,036)
Changes in Stockholders' Equity
Comprehensive income		155,283						140,077	15,206
Cash dividends declared and paid, $0.82 and $0.79 per share at September 30, 2017 and 2016, respectively		(58,504)						(58,504)
Net shares issued under share-based compensation plans			$ (23,448)		$ 553		$ (24,001)
Share-based compensation expense		14,573		0		14,573
Ending balance at Sep. 30, 2017		2,673,089		71,152		2,201,334		425,433	(24,830)
Beginning balance at Jun. 30, 2017									(34,129)
Changes in Stockholders' Equity
Comprehensive income		49,758
Ending balance at Sep. 30, 2017		$ 2,673,089		$ 71,152		$ 2,201,334		$ 425,433	$ (24,830)

[1] Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 8, Loan Servicing Rights, for further details on the changes in accounting policy.