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
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

[1] Market value of plan assets reflects any contributions received through June 30, 2015, or 2014, respectively.