Investments - Schedule of Investments in Limited Partnerships (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Schedule of Cost-method Investments
Other investments, cost	$ 535,560	$ 527,183
Unrealized Loss	(3,947)	(6,134)
Unrealized Gain	9,493	7,598
Other Long-term Investments
Schedule of Cost-method Investments
Total other investments	14,728
Other investments, cost	14,618	5,493
Fair value - partnerships	14,943
Other Long-term Investments	14,943	5,733
Unrealized Loss	(20)	(27)
Unrealized Gain	345	$ 267
Net unrealized gain (loss)	345
Limited Partnership | Other Long-term Investments
Schedule of Cost-method Investments
Initial investment - partnerships	14,428
Other investments, cost	14,318
Fair value - partnerships	14,643
Unrealized Loss	(20)
Net unrealized gain (loss)	345
Limited Partnership | Other Long-term Investments | Level 2
Schedule of Cost-method Investments
Initial investment - partnerships	13,116
Other investments, cost	12,977
Fair value - partnerships	12,977
Unrealized Loss	0
Net unrealized gain (loss)	0
Limited Partnership | Other Long-term Investments | Level 3
Schedule of Cost-method Investments
Initial investment - partnerships	1,312
Other investments, cost	1,341
Fair value - partnerships	1,666
Unrealized Loss	(20)
Net unrealized gain (loss)	345
Certificates of Deposit | Other Long-term Investments | Level 1
Schedule of Cost-method Investments
Initial investment - certificates of deposit	300
Other investments, cost	300
Fair value - certificates of deposit	300
Unrealized Loss	0
Unrealized Gain	0
DCR Mortgage Fund VI, L.P. | Limited Partnership | Other Long-term Investments | Level 3
Schedule of Cost-method Investments
Initial investment - partnerships	312
Other investments, cost	360
Fair value - partnerships	705
Unrealized Loss	0
Unrealized Gain	345
RCH Mortgage Fund VI, L.P. | Limited Partnership | Other Long-term Investments | Level 3
Schedule of Cost-method Investments
Initial investment - partnerships	1,000
Other investments, cost	981
Fair value - partnerships	961
Unrealized Loss	(20)
Unrealized Gain	0
Kayne Senior Credit Fund II, L.P. | Limited Partnership | Other Long-term Investments | Level 2
Schedule of Cost-method Investments
Initial investment - partnerships	1,658
Other investments, cost	1,509
Fair value - partnerships	1,509
Unrealized Loss	0
Unrealized Gain	0
DCR Mortgage Fund VII, L.P. | Limited Partnership | Other Long-term Investments | Level 2
Schedule of Cost-method Investments
Initial investment - partnerships	2,000
Other investments, cost	2,010
Fair value - partnerships	2,010
Unrealized Loss	0
Unrealized Gain	0
Blackstone Alternative Solutions Trust 2015 | Limited Partnership | Other Long-term Investments | Level 2
Schedule of Cost-method Investments
Initial investment - partnerships	335
Other investments, cost	335
Fair value - partnerships	335
Unrealized Loss	0
Unrealized Gain	0
Green Street Power Partners | Limited Partnership | Other Long-term Investments | Level 2
Schedule of Cost-method Investments
Initial investment - partnerships	9,123
Other investments, cost	9,123
Fair value - partnerships	9,123
Unrealized Loss	0
Unrealized Gain	$ 0