Loans Receivable - Schedule of Changes in the Accretable Yield for Acquired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016
Credit Impaired Acquired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period, accretable yield	$ 58,842	$ 72,705
Balance at beginning of period, carrying amount of loans	91,761	111,300
Additions, accretable yield	0	0
Additions, carrying amount of loans	0	0
Reclassification from nonaccretable balance, net, accretable yield	0	4,867
Reclassification from nonaccretable balance, net, carrying value of loans	0	0
Accretion, accretable yield	(3,233)	(18,730)
Accretion	3,233	18,730
Transfers to REO, accretable yield	0	0
Transfers to REO, carrying amount of loans	0	(175)
Payments received, net, accretable yield	0	0
Payments received, net, carrying amount of loans	(16,852)	(38,094)
Balance at end of period, accretable yield	55,609	58,842
Balance at end of period, carrying amount of loans	78,142	91,761
Acquired Non Impaired Loans
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period, accretable yield	4,222	7,204
Balance at beginning of period, carrying amount of loans	131,132	187,080
Additions, accretable yield	0	0
Additions, carrying amount of loans	0	0
Reclassification from nonaccretable balance, net, accretable yield	0	0
Reclassification from nonaccretable balance, net, carrying value of loans	0	0
Accretion, accretable yield	(198)	(2,982)
Accretion	198	2,982
Transfers to REO, accretable yield	0	0
Transfers to REO, carrying amount of loans	0	0
Payments received, net, accretable yield	0	0
Payments received, net, carrying amount of loans	5,211	(58,930)
Balance at end of period, accretable yield	4,024	4,222
Balance at end of period, carrying amount of loans	$ 136,541	$ 131,132