Loans Receivable and Allowance for Loan Losses (Schedule of Allowance for Loan Losses by Portfolio Segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 60,195	$ 61,883
Provision charged (credited) to operations	5,400	1,500
Recoveries of loans previously charged-off	395	687
Loans charged-off	(3,469)	(1,915)
Balance at end of period	62,521	62,155
Mortgage Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	28,052	29,626
Provision charged (credited) to operations	(22)	(130)
Recoveries of loans previously charged-off	88	53
Loans charged-off	(117)	(231)
Balance at end of period	28,001	29,318
Commercial Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	29,814	29,143
Provision charged (credited) to operations	5,390	1,616
Recoveries of loans previously charged-off	127	458
Loans charged-off	(3,005)	(1,431)
Balance at end of period	32,326	29,786
Consumer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	2,329	3,114
Provision charged (credited) to operations	32	14
Recoveries of loans previously charged-off	180	176
Loans charged-off	(347)	(253)
Balance at end of period	$ 2,194	$ 3,051