Capital Stock - Dividends (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Dividends [Line Items]
Per Share Amount	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 0.42	$ 0.54	$ 0.54	$ 1.68	$ 1.92	$ 2.16
Dividends Common Stock Cash									$ (41,388,000)	$ (38,748,000)	$ (22,643,000)
Year 2014
Cash Dividends [Line Items]
Per Share Amount											$ 2.16
Dividends Common Stock Cash											$ 22,643,000
Year 2015
Cash Dividends [Line Items]
Per Share Amount										$ 1.92
Dividends Common Stock Cash										$ 38,748,000
Year 2016
Cash Dividends [Line Items]
Per Share Amount									$ 1.68
Dividends Common Stock Cash									$ 41,388,000
Year 2017
Cash Dividends [Line Items]
Per Share Amount									$ 0.28
Dividends Common Stock Cash									$ 9,245,000