Equity Method Investments - Activity Related to Equity Method Investments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Equity Method Investments
Balance at beginning of period	$ 163,181	$ 86,077
Contributions	1,828	35,418
Distributions	(4,729)	0
Earnings (loss) on equity method investments	3,684	(994)
Balance at end of period	$ 163,964	120,501
Constitution
Schedule of Equity Method Investments [Line Items]
Ownership percentage	25.00%
Equity Method Investments
Balance at beginning of period	$ 0	732
Contributions	250	250
Distributions	0	0
Earnings (loss) on equity method investments	(250)	(982)
Balance at end of period	$ 0	0
Meade
Schedule of Equity Method Investments [Line Items]
Ownership percentage	20.00%
Equity Method Investments
Balance at beginning of period	$ 163,181	85,345
Contributions	1,578	35,168
Distributions	(4,729)	0
Earnings (loss) on equity method investments	3,934	(12)
Balance at end of period	$ 163,964	$ 120,501

Equity Method Investments [Roll Forward]

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Amount of distribution received from equity method investee for return on investment, classified as operating activities. Excludes distribution for return of investment, classified as investing activities.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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The cash outflow associated with the purchase of or advances to an equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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