Goodwill and intangibles (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 444,327,000		$ 444,327,000			$ 212,820,000
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	2,597,000		2,597,000
Finite-Lived Intangible Assets, Net	52,837,000	$ 8,935,000	52,837,000	$ 8,935,000	$ 9,018,000	$ 9,648,000	$ 9,762,000	$ 10,589,000
Finite-lived Intangible Assets Acquired	47,950,000	0	47,950,000	0
Finite-Lived Intangible Assets, Period Increase (Decrease)	(3,069,000)	0	(3,069,000)	0
Core deposit intangibles amortization	(1,062,000)	$ (827,000)	(1,692,000)	$ (1,654,000)
Finite-Lived Intangible Assets, Amortization Expense, Year Two	5,093,000		5,093,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	4,994,000		4,994,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	4,872,000		4,872,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	4,729,000		4,729,000
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	22,164,000		22,164,000
Goodwill, Impairment Loss			0
Bank of the Cascades [Member]
Goodwill [Line Items]
Goodwill	$ 231,500		$ 231,500