Common Stock - Narrative (Details)	3 Months Ended												12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2019 USD ($) vote $ / shares shares	Dec. 31, 2018 USD ($) vote $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Mar. 31, 2020 $ / shares	Feb. 11, 2020 USD ($)
Equity [Abstract]
Common stock, shares authorized (in shares) | shares	500,000,000				500,000,000								500,000,000	500,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001				$ 0.001								$ 0.001	$ 0.001
Number of votes entitled | vote													1	1
Dividends per Common Share (in dollars per share) | $ / shares	$ 0.14	$ 0.14	$ 0.14	$ 0.14	$ 0.13	$ 0.13	$ 0.13	$ 0.13	$ 0.12	$ 0.12	$ 0.12	$ 0.12	$ 0.56	$ 0.52	$ 0.48
Amount	$ 10,718,000	$ 10,726,000	$ 10,751,000	$ 10,782,000	$ 9,968,000	$ 9,954,000	$ 9,917,000	$ 9,917,000	$ 9,098,000	$ 9,146,000	$ 9,149,000	$ 9,152,000	$ 42,977,000	$ 39,756,000	$ 36,545,000
Dividends Payable [Line Items]
Issued and outstanding common stock authorized to repurchase	50,000,000.0												50,000,000.0
Aggregate purchases of shares in open market before shares will be purchased from Magnus	$ 24,900,000												$ 24,900,000
Shares repurchased (in shares) | shares													1,127,966
Average price (in dollars per share) | $ / shares													$ 26.02
Purchases of common stock													$ 29,352,000
Accrued share repurchase (in shares) | shares	56,000												56,000
Amount remaining under current authorizations	$ 20,600,000												$ 20,600,000
Magnus
Dividends Payable [Line Items]
Shares repurchased (in shares) | shares													535,983
Average price (in dollars per share) | $ / shares													$ 25.70
Purchases of common stock													$ 13,775,000
Share repurchase liability	$ 1,800,000												$ 1,800,000
Accrued share repurchase (in shares) | shares	56,000												56,000
Amount remaining under current authorizations	$ 11,100,000												$ 11,100,000
Forecast
Dividends Payable [Line Items]
Dividends declared (in dollars per share) | $ / shares																$ 0.155
Subsequent Event
Dividends Payable [Line Items]
Issued and outstanding common stock authorized to repurchase																	$ 100,000,000.0
Additional issued and outstanding common stock authorized to repurchase																	$ 50,000,000.0