Fair Value Measurements - Financial instruments not carried at fair value (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments	$ 142,500	$ 142,300
Deposit liabilities	1,121,194	1,116,233
Notes payable and debt	2,648,353	2,647,677
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments	142,523	142,271
Deposit liabilities	1,121,194	1,116,233
Notes payable and debt	2,648,353	2,647,677
Financial Liabilities	3,769,547	3,763,910
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments	154,262	153,173
Deposit liabilities	1,387,944	1,337,406
Notes payable and debt	2,870,898	2,813,257
Financial Liabilities	$ 4,258,842	$ 4,150,663