Pension and Severance Plans (Tables)

12 Months Ended

Dec. 31, 2016

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Schedule Of Accrued Severance Obligation

The changes to the balance of our severance accrual are as follows:

	For the Year Ended December 31,
	2016			2015			2014
	(In thousands)
Balance at the beginning of year	$	143,151		$	146,880		$	145,373
Provision of severance benefits	6,746			21,088			17,593
Severance payments	(9,429		)	(15,021		)	(10,160		)
(Gain) loss on foreign currency	(4,072		)	(9,796		)	(5,926		)
	136,396			143,151			146,880
Payments remaining with the National Pension Fund	(182		)	(192		)	(219		)
Total severance obligation balance at the end of year	136,214			142,959			146,661
Less current portion of accrued severance obligation (Note 12)	14,053			14,306			13,226
Non-current portion of severance obligation	$	122,161		$	128,653		$	133,435

Schedule of Changes in Projected Benefit Obligations and Fair Value of Plan Assets

The following table summarizes the Plans’ benefit obligations, fair value of the Plans’ assets and the funded status of the Plans at December 31, 2016 and 2015.

	For the Year Ended December 31,
	2016			2015
	(In thousands)
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$	109,695		$	74,009
Service cost	33,854			12,481
Interest cost	3,641			2,954
Benefits paid	(8,499		)	(3,924		)
Actuarial (gain) loss	(2,801		)	(2,631		)
Acquisition (Note 3)	—			31,859
Settlement	(1,165		)	—
Foreign exchange (gain) loss	(3,309		)	(5,053		)
Projected benefit obligation at end of year	131,416			109,695
Change in plan assets:
Fair value of plan assets at beginning of year	76,042			54,771
Actual gain (loss) on plan assets	2,876			1,564
Employer contributions	25,114			12,190
Acquisition (Note 3)	—			13,935
Settlement	(1,165		)	—
Benefits paid	(8,499		)	(3,924		)
Foreign exchange gain (loss)	(2,897		)	(2,494		)
Fair value of plan assets at end of year	91,471			76,042
Funded status of the Plans at end of year	$	(39,945	)	$	(33,653	)

Schedule of Amounts Recognized in Other Comprehensive Income (Loss)

The following table summarizes, by component, the change in accumulated other comprehensive income (loss) related to our Plans:

	Prior Service Cost		Actuarial Net Gain (Loss)			Total
	(In thousands)
Balance at December 31, 2014, net of tax	$	540	$	(3,065	)	$	(2,525	)
Amortization included in net periodic pension cost	20		68			88
Net gain (loss) arising during period	—		1,012			1,012
Adjustments to unrealized components of defined benefit pension plan included in other comprehensive income (loss)	20		1,080			1,100
Balance at December 31, 2015, net of tax	$	560	$	(1,985	)	$	(1,425	)
Amortization included in net periodic pension cost	22		73			95
Net gain (loss) arising during period	—		2,468			2,468
Adjustments to unrealized components of defined benefit pension plan included in other comprehensive income (loss)	22		2,541			2,563
Balance at December 31, 2016, net of tax	$	582	$	556		$	1,138
Estimated amortization of cost to be included in 2017 net periodic pension cost	$	30	$	84		$	114

Schedule of Benefit Obligations in Excess of Fair Value of Plan Assets

Information for pension plans with benefit obligations in excess of plan assets are as follows:

	December 31,
	2016		2015
	(In thousands)
Plans with underfunded or non-funded projected benefit obligation:
Aggregate projected benefit obligation	$	131,416	$	101,832
Aggregate fair value of plan assets	91,471		67,622
Plans with underfunded or non-funded accumulated benefit obligation:
Aggregate accumulated benefit obligation	49,285		40,428
Aggregate fair value of plan assets	16,811		13,944

Components of net periodic pension cost

The following table summarizes net periodic pension costs:

	For the Year Ended December 31,
	2016			2015			2014
	(In thousands)
Components of net periodic pension cost and total pension expense:
Service cost	$	33,854		$	12,481		$	5,042
Interest cost	3,641			2,954			3,051
Expected return on plan assets	(3,788		)	(3,330		)	(3,094		)
Amortization of prior service cost	35			34			116
Recognized actuarial (gain) loss	94			91			141
Net periodic pension cost	33,836			12,230			5,256
Settlement (gain) loss	128			27			97
Total pension expense	$	33,964		$	12,257		$	5,353

Schedule of Assumptions Used

The following table summarizes the weighted-average assumptions used in computing the net periodic pension cost and projected benefit obligation at December 31, 2016, 2015 and 2014:

	For the Year Ended December 31,
	2016		2015		2014
Discount rate for determining net periodic pension cost	3.3	%	4.2	%	3.9	%
Discount rate for determining benefit obligations at year end	3.1	%	3.3	%	4.2	%
Rate of compensation increase for determining net periodic pension cost	3.9	%	4.7	%	4.1	%
Rate of compensation increase for determining benefit obligations at year end	3.8	%	3.9	%	4.7	%
Expected rate of return on plan assets for determining net periodic pension cost	5.0	%	6.2	%	6.2	%

Schedule of Allocation of Plan Assets

The current rate of return assumption targets are based on asset allocation strategies as follows:

	Allocation
	Debt		Equity		Other
Japan defined benefit plan	59	%	39	%	2	%
Korea defined benefit plan	40	%	50	%	10	%
Philippine defined benefit plan	40	%	56	%	4	%

Philippine plan assets included Amkor common stock of $0.6 million at December 31, 2015. The common stock was sold in 2016.

The fair value of our pension plan assets, by asset category utilizing the fair value hierarchy as discussed in Note 16, is as follows:

	December 31,
	2016		2015
	(In thousands)
Cash and cash equivalents (Level 1)	$	10,419	$	14,944
Equity securities
U.S. securities (Level 1)	12,602		19,501
Foreign securities (Level 1)	8,825		10,689
Foreign mutual funds (Level 1)	12,718		—
	34,145		30,190
Fixed income funds (Level 1)	—		3,492
Debt securities
U.S. government bonds (Level 1)	2,859		2,187
U.S. corporate bonds (Level 1)	1,980		—
Foreign government bonds (Level 1)	11,001		880
Foreign government bonds (Level 2)	7,727		8,092
Foreign corporate bonds (Level 2)	1,693		—
Foreign treasury notes (Level 1)	—		6,665
Foreign mutual funds (Level 1)	10,044		—
	35,304		17,824
Foreign guaranteed investment contracts (Level 3)	2,445		842
Taiwan retirement fund (Level 1)	8,972		8,621
Other (Level 2)	186		129
Total	$	91,471	$	76,042

Schedule of Expected Benefit Payments

The estimated future benefit payments related to our foreign defined benefit plans are as follows:

	Payments
	(In thousands)
2017	$	6,884
2018	5,748
2019	7,638
2020	9,579
2021	11,540
2022 to 2026	91,261