Fair Value Measurements - Financial instruments not carried at fair value (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments		$ 148,600	$ 142,300
Deposit liabilities		1,123,628	1,116,233
Notes payable and debt	[1]	3,207,339	2,647,677
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments		148,634	142,271
Deposit liabilities		1,123,628	1,116,233
Notes payable and debt		3,243,800	2,647,677
Financial Liabilities		4,367,428	3,763,910
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments		158,585	153,173
Deposit liabilities		1,365,910	1,337,406
Notes payable and debt		3,494,523	2,813,257
Financial Liabilities		$ 4,860,433	$ 4,150,663

[1] "In Use/Outstanding" data represent June 30, 2017 and December 31, 2016 accreted values.