Investments (Unconsolidated Subsidiaries) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	$ 401,030	$ 330,591
Qualified affordable housing project tax credit partnerships
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	80,507	84,607
Other tax credit partnerships
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	5,735	6,118
All other investments, primarily investment fund LPs/LLCs
Unconsolidated Subsidiaries
Investment in unconsolidated subsidiaries	$ 314,788	$ 239,866