Schedule I - Condensed Financial Information of the Registrant - Condensed Balance Sheet (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
ASSETS
Cash and cash equivalents		$ 41,091	$ 43,920	$ 71,618	$ 24,244
Total assets	[1]	4,408,352	4,697,447
Liabilities and Equity [Abstract]
Total liabilities	[2]	2,935,935	3,162,545
Stockholders' equity:
Preferred stock (no par value): authorized 50,000,000 shares; none outstanding		0	0
Accumulated other comprehensive loss		(31,224)	(36,445)
Retained earnings		174,039	214,582
Total stockholders' equity		1,447,970	1,500,421	736,981	$ 286,949
Total liabilities and stockholders' equity		4,408,352	4,697,447
Parent Company [Member]
ASSETS
Cash and cash equivalents		0	2,388	$ 0
Advances to and investment in consolidated subsidiaries		1,447,970	1,498,033
Total assets		1,447,970	1,500,421
Liabilities and Equity [Abstract]
Total liabilities		0	0
Stockholders' equity:
Accumulated other comprehensive loss		(31,224)	(36,445)
Retained earnings		174,039	214,582
Total stockholders' equity		1,447,970	1,500,421
Total liabilities and stockholders' equity		1,447,970	1,500,421
Voting Common Stock [Member]
Stockholders' equity:
Voting common stock, authorized 400,000,000 shares; issued 128,600,384 and129,931,812, Non-voting common stock, authorized 400,000,000 shares, none outstanding		1,305,155	1,322,284
Voting Common Stock [Member] | Parent Company [Member]
Stockholders' equity:
Preferred stock (no par value): authorized 50,000,000 shares; none outstanding		0	0
Voting common stock, authorized 400,000,000 shares; issued 128,600,384 and129,931,812, Non-voting common stock, authorized 400,000,000 shares, none outstanding		1,305,155	1,322,284
Nonvoting Common Stock [Member]
Stockholders' equity:
Voting common stock, authorized 400,000,000 shares; issued 128,600,384 and129,931,812, Non-voting common stock, authorized 400,000,000 shares, none outstanding		0	0
Nonvoting Common Stock [Member] | Parent Company [Member]
Stockholders' equity:
Voting common stock, authorized 400,000,000 shares; issued 128,600,384 and129,931,812, Non-voting common stock, authorized 400,000,000 shares, none outstanding		$ 0	$ 0

[1] Consolidated assets as of December 31, 2015, and 2014, include total assets of variable interest entities (VIEs) of $145 million and $151 million, respectively, which can only be used to settle the obligations of the VIEs. See Note 1: Summary of Significant Accounting Policies.

[2] Consolidated liabilities as of December 31, 2015, and 2014, include total liabilities of VIEs of $39 million and $43 million, respectively, for which the creditors of the VIEs have no recourse to the Company, except for certain of the debt, which the Company guarantees. See Note 1 and Note 4.