Securities (Tables)

12 Months Ended

Dec. 31, 2016

Schedule of Available-for-sale Securities [Line Items]

Securities Available for Sale

The following table summarizes the amortized cost, gross unrealized gains and losses and the resulting fair value of securities available for sale:

	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
December 31, 2016	(in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,486,690	$	2,760	$	(23,718	)	$	1,465,732
State and municipal securities	473,914		6,343		(5,197		)	475,060
U.S. government agency and government-sponsored enterprise securities	332,348		1,065		(1,511		)	331,902
U.S. government securities	801		—		(1		)	800
Other securities	5,284		63		(264		)	5,083
Total	$	2,299,037	$	10,231	$	(30,691	)	$	2,278,577
December 31, 2015
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,296,955	$	4,525	$	(14,991	)	$	1,286,489
State and municipal securities	480,417		12,690		(938		)	492,169
U.S. government agency and government-sponsored enterprise securities	354,515		1,113		(1,846		)	353,782
U.S. government securities	20,439		—		(302		)	20,137
Other securities	5,284		24		(191		)	5,117
Total	$	2,157,610	$	18,352	$	(18,268	)	$	2,157,694

Schedule of gross realized gains and losses on sales and calls of securities available for sale [Table Text Block]

The following table provides the gross realized gains and losses on the sales and calls of securities for the periods indicated:

	Years Ended December 31,
	2016		2015			2014
	(in thousands)
Gross realized gains	$	1,181	$	1,591		$	553
Gross realized losses	—		(10		)	(1		)
Net realized gains	$	1,181	$	1,581		$	552

Schedule of Contractual Maturities of Investment Securities Available for Sale

The scheduled contractual maturities of investment securities available for sale at December 31, 2016 are presented as follows:

	December 31, 2016
	Amortized Cost		Fair Value
	(in thousands)
Due within one year	$	38,596	$	38,717
Due after one year through five years	515,056		517,283
Due after five years through ten years	679,739		672,018
Due after ten years	1,060,362		1,045,476
Other securities with no stated maturity	5,284		5,083
Total investment securities available-for-sale	$	2,299,037	$	2,278,577

Schedule of Securities pledged as collateral [Table Text Block]

The following table summarizes the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:

	December 31, 2016		December 31, 2015
	(in thousands)
Washington and Oregon State to secure public deposits	$	232,714	$	341,079
Federal Reserve Bank to secure borrowings	33,825		48,714
Other securities pledged	132,350		143,606
Total securities pledged as collateral	$	398,889	$	533,399

Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses

The following tables show the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2016 and 2015:

	Less than 12 Months					12 Months or More					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
December 31, 2016	(in thousands)
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,029,116	$	(18,788	)	$	159,046	$	(4,930	)	$	1,188,162	(23,718		)
State and municipal securities	211,342		(5,064		)	3,384		(133		)	214,726		(5,197		)
U.S. government agency and government-sponsored enterprise securities	218,811		(1,511		)	—		—			218,811		(1,511		)
U.S. government securities	251		(1		)	—		—			251		(1		)
Other securities	2,263		(51		)	2,743		(213		)	5,006		(264		)
Total	$	1,461,783	$	(25,415	)	$	165,173	$	(5,276	)	$	1,626,956	$	(30,691	)
December 31, 2015
U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	664,509	$	(7,610	)	$	214,325	$	(7,381	)	$	878,834	$	(14,991	)
State and municipal securities	48,261		(358		)	31,383		(580		)	79,644		(938		)
U.S. government agency and government-sponsored enterprise securities	193,400		(1,128		)	40,034		(718		)	233,434		(1,846		)
U.S. government securities	10,343		(136		)	9,794		(166		)	20,137		(302		)
Other securities	2,300		(15		)	2,780		(176		)	5,080		(191		)
Total	$	918,813	$	(9,247	)	$	298,316	$	(9,021	)	$	1,217,129	$	(18,268	)