Investments - Investments in Unconsolidated Subsidiaries Narrative (Details) $ in Thousands	Dec. 31, 2016 USD ($) Business investment_interest	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 204,719	$ 162,624
Investment in unconsolidated subsidiaries	$ 340,906	311,908
Number of LPs / LLCs with investment ownership percent over 25% | Business	3
Tax Credit Partnerships Almost 100% Ownership
Schedule of Available-for-sale Securities [Line Items]
Number of tax credit partnerships almost 100% ownership percentage | investment_interest	2
Investment in unconsolidated subsidiaries	$ 40,200
Tax Credit Partnerships Almost 100% Ownership | Maximum
Schedule of Available-for-sale Securities [Line Items]
Percentage ownership (greater than) (percent)	100.00%
Tax Credit Partnerships Less Than 20% Ownership
Schedule of Available-for-sale Securities [Line Items]
Investment in unconsolidated subsidiaries	$ 62,100
Tax Credit Partnerships Less Than 20% Ownership | Maximum
Schedule of Available-for-sale Securities [Line Items]
Percentage ownership (greater than) (percent)	20.00%
Other Limited Partnership and Limited Liability Company Not Considered Investment Funds
Schedule of Available-for-sale Securities [Line Items]
Investment in unconsolidated subsidiaries	$ 22,400	$ 19,400
Other Limited Partnerships and Limited Liability Company, Greater Than 25 Percent Ownership
Schedule of Available-for-sale Securities [Line Items]
Percentage ownership (greater than) (percent)	25.00%
Investment in unconsolidated subsidiaries	$ 18,500
Other Limited Partnerships and Limited Liability Company Less than 25% Ownership
Schedule of Available-for-sale Securities [Line Items]
Percentage ownership (greater than) (percent)	25.00%
Investment in unconsolidated subsidiaries	$ 208,600