Stock Based Compensation - RSUs under the Subsidiary Incentive Plans Rollforward (Details) - Subsidiary Incentive Plan - Restricted Stock Units (RSUs) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested balance, beginning of period	$ 8,710	$ 8,792	$ 8,089
Granted	0	1,113	2,669
Vested	(4,991)	(1,771)	(2,436)
Grant value adjustment (1)			(210)
Performance assumption adjustment	560	576	680
Unvested balance, end of period	$ 4,279	$ 8,710	$ 8,792
Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Vested Shares, If Converted	891,933
Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Nonvested Shares, If Converted	2,529,709