Benefit Plans Multiemployer Pension Plans (Details) - USD ($) |
12 Months Ended | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Nov. 28, 2014 |
Sep. 25, 2014 |
Dec. 20, 2013 |
Dec. 05, 2013 |
Sep. 18, 2013 |
Dec. 04, 2012 |
Oct. 29, 2012 |
Nov. 22, 2011 |
Dec. 31, 2015 |
Dec. 31, 2014 |
Jun. 30, 2014 |
Dec. 31, 2013 |
Jun. 30, 2012 |
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| Multiemployer Plans [Line Items] | ||||||||||||||||
| First Financial Northwest's Plan(1) | 102.80% | [1] | 105.30% | |||||||||||||
| Deferred compensation expense | $ 101,000 | $ 170,000 | $ 159,000 | |||||||||||||
| Pentegra DB Plan | ||||||||||||||||
| Multiemployer Plans [Line Items] | ||||||||||||||||
| Contributions by employer | $ 540,000,000 | $ 539,932,000 | $ 8,735,000 | $ 43,979,000 | $ 26,328,000 | $ 159,080,000 | $ 540,000,000 | $ 548,667,000 | $ 229,387,000 | |||||||
| Multiemployer Plans, Pension | Pentegra DB Plan | ||||||||||||||||
| Multiemployer Plans [Line Items] | ||||||||||||||||
| Assumptions used calculating net periodic benefit cost | 6.28% | 6.49% | ||||||||||||||
| Maximum contribution rate | 5.00% | |||||||||||||||
| Total contributions made to plan | $ 190,800,000 | $ 136,500,000 | ||||||||||||||
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